diff --git a/samples/ConditionalFormatting/cond09_iconset.php b/samples/ConditionalFormatting/cond09_iconset.php
new file mode 100644
index 0000000000..61239b01c7
--- /dev/null
+++ b/samples/ConditionalFormatting/cond09_iconset.php
@@ -0,0 +1,110 @@
+<?php
+
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheet\Style\Conditional;
+use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalFormatValueObject;
+use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalIconSet;
+use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\IconSetValues;
+
+require __DIR__ . '/../Header.php';
+/** @var PhpOffice\PhpSpreadsheet\Helper\Sample $helper */
+
+// Create new Spreadsheet object
+$helper->log('Create new Spreadsheet object');
+$spreadsheet = new Spreadsheet();
+$sheet = $spreadsheet->getActiveSheet();
+
+// Set document properties
+$helper->log('Set document properties');
+$spreadsheet->getProperties()->setCreator('issakujitsuk')
+    ->setLastModifiedBy('issakujitsuk')
+    ->setTitle('PhpSpreadsheet Test Document')
+    ->setSubject('PhpSpreadsheet Test Document')
+    ->setDescription('Test document for PhpSpreadsheet, generated using PHP classes.')
+    ->setKeywords('office PhpSpreadsheet php')
+    ->setCategory('Test result file');
+
+// Create the worksheet
+$helper->log('Add data');
+foreach (['A', 'B', 'C'] as $columnIndex) {
+    $sheet
+        ->setCellValue("{$columnIndex}1", 1)
+        ->setCellValue("{$columnIndex}2", 2)
+        ->setCellValue("{$columnIndex}3", 8)
+        ->setCellValue("{$columnIndex}4", 4)
+        ->setCellValue("{$columnIndex}5", 5)
+        ->setCellValue("{$columnIndex}6", 6)
+        ->setCellValue("{$columnIndex}7", 7)
+        ->setCellValue("{$columnIndex}8", 3)
+        ->setCellValue("{$columnIndex}9", 9)
+        ->setCellValue("{$columnIndex}10", 10);
+}
+
+// Set conditional formatting rules and styles
+$helper->log('Define conditional formatting using Icon Set');
+
+// 3 icons
+$sheet->getStyle('A1:A10')
+    ->setConditionalStyles([
+        makeConditionalIconSet(
+            IconSetValues::ThreeSymbols,
+            [
+                new ConditionalFormatValueObject('percent', 0),
+                new ConditionalFormatValueObject('percent', 33),
+                new ConditionalFormatValueObject('percent', 67),
+            ]
+        ),
+    ]);
+
+// 4 icons
+$sheet->getStyle('B1:B10')
+    ->setConditionalStyles([
+        makeConditionalIconSet(
+            IconSetValues::FourArrows,
+            [
+                new ConditionalFormatValueObject('percent', 0),
+                new ConditionalFormatValueObject('percent', 25),
+                new ConditionalFormatValueObject('percent', 50),
+                new ConditionalFormatValueObject('percent', 75),
+            ]
+        ),
+    ]);
+
+// 5 icons
+$sheet->getStyle('C1:C10')
+    ->setConditionalStyles([
+        makeConditionalIconSet(
+            IconSetValues::FiveQuarters,
+            [
+                new ConditionalFormatValueObject('percent', 0),
+                new ConditionalFormatValueObject('percent', 20),
+                new ConditionalFormatValueObject('percent', 40),
+                new ConditionalFormatValueObject('percent', 60),
+                new ConditionalFormatValueObject('percent', 80),
+            ]
+        ),
+    ]);
+
+// Save
+$sheet->setSelectedCells('A1');
+$helper->write($spreadsheet, __FILE__, ['Xlsx']);
+
+/**
+ * Helper function to create a Conditional object with an IconSet.
+ *
+ * @param IconSetValues $type The type of icon set
+ * @param ConditionalFormatValueObject[] $cfvos The conditional format value objects
+ */
+function makeConditionalIconSet(
+    IconSetValues $type,
+    array $cfvos,
+): Conditional {
+    $condition = new Conditional();
+    $condition->setConditionType(Conditional::CONDITION_ICONSET);
+    $iconSet = new ConditionalIconSet();
+    $condition->setIconSet($iconSet);
+    $iconSet->setIconSetType($type)
+        ->setCfvos($cfvos);
+
+    return $condition;
+}
diff --git a/src/PhpSpreadsheet/Reader/Xlsx/ConditionalStyles.php b/src/PhpSpreadsheet/Reader/Xlsx/ConditionalStyles.php
index b09de2ad69..2892dd1225 100644
--- a/src/PhpSpreadsheet/Reader/Xlsx/ConditionalStyles.php
+++ b/src/PhpSpreadsheet/Reader/Xlsx/ConditionalStyles.php
@@ -9,6 +9,8 @@
 use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalDataBar;
 use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalFormattingRuleExtension;
 use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalFormatValueObject;
+use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalIconSet;
+use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\IconSetValues;
 use PhpOffice\PhpSpreadsheet\Style\Style as Style;
 use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
 use SimpleXMLElement;
@@ -265,6 +267,8 @@ private function readStyleRules(array $cfRules, SimpleXMLElement $extLst): array
                 $objConditional->setColorScale(
                     $this->readColorScale($cfRule)
                 );
+            } elseif (isset($cfRule->iconSet)) {
+                $objConditional->setIconSet($this->readIconSet($cfRule));
             } elseif (isset($cfRule['dxfId'])) {
                 $objConditional->setStyle(clone $this->dxfs[(int) ($cfRule['dxfId'])]);
             }
@@ -349,6 +353,40 @@ private function readColorScale(SimpleXMLElement|stdClass $cfRule): ConditionalC
         return $colorScale;
     }
 
+    private function readIconSet(SimpleXMLElement $cfRule): ConditionalIconSet
+    {
+        $iconSet = new ConditionalIconSet();
+
+        if (isset($cfRule->iconSet['iconSet'])) {
+            $iconSet->setIconSetType(IconSetValues::from($cfRule->iconSet['iconSet']));
+        }
+        if (isset($cfRule->iconSet['reverse'])) {
+            $iconSet->setReverse('1' === (string) $cfRule->iconSet['reverse']);
+        }
+        if (isset($cfRule->iconSet['showValue'])) {
+            $iconSet->setShowValue('1' === (string) $cfRule->iconSet['showValue']);
+        }
+        if (isset($cfRule->iconSet['custom'])) {
+            $iconSet->setCustom('1' === (string) $cfRule->iconSet['custom']);
+        }
+
+        $cfvos = [];
+        foreach ($cfRule->iconSet->cfvo as $cfvoXml) {
+            $type = (string) $cfvoXml['type'];
+            $value = (string) ($cfvoXml['val'] ?? '');
+            $cfvo = new ConditionalFormatValueObject($type, $value);
+            if (isset($cfvoXml['gte'])) {
+                $cfvo->setGreaterThanOrEqual('1' === (string) $cfvoXml['gte']);
+            }
+            $cfvos[] = $cfvo;
+        }
+        $iconSet->setCfvos($cfvos);
+
+        // TODO: The cfIcon element is not implemented yet.
+
+        return $iconSet;
+    }
+
     /** @param ConditionalFormattingRuleExtension[] $conditionalFormattingRuleExtensions */
     private function readDataBarExtLstOfConditionalRule(ConditionalDataBar $dataBar, SimpleXMLElement $cfRule, array $conditionalFormattingRuleExtensions): void
     {
diff --git a/src/PhpSpreadsheet/Style/Conditional.php b/src/PhpSpreadsheet/Style/Conditional.php
index 2ef7cacd79..fedd0aa486 100644
--- a/src/PhpSpreadsheet/Style/Conditional.php
+++ b/src/PhpSpreadsheet/Style/Conditional.php
@@ -5,6 +5,7 @@
 use PhpOffice\PhpSpreadsheet\IComparable;
 use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalColorScale;
 use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalDataBar;
+use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalIconSet;
 
 class Conditional implements IComparable
 {
@@ -25,6 +26,7 @@ class Conditional implements IComparable
     const CONDITION_TIMEPERIOD = 'timePeriod';
     const CONDITION_DUPLICATES = 'duplicateValues';
     const CONDITION_UNIQUE = 'uniqueValues';
+    const CONDITION_ICONSET = 'iconSet';
 
     private const CONDITION_TYPES = [
         self::CONDITION_BEGINSWITH,
@@ -43,6 +45,7 @@ class Conditional implements IComparable
         self::CONDITION_NOTCONTAINSTEXT,
         self::CONDITION_TIMEPERIOD,
         self::CONDITION_UNIQUE,
+        self::CONDITION_ICONSET,
     ];
 
     // Operator types
@@ -102,6 +105,8 @@ class Conditional implements IComparable
 
     private ?ConditionalColorScale $colorScale = null;
 
+    private ?ConditionalIconSet $iconSet = null;
+
     private Style $style;
 
     private bool $noFormatSet = false;
@@ -318,6 +323,18 @@ public function setColorScale(ConditionalColorScale $colorScale): static
         return $this;
     }
 
+    public function getIconSet(): ?ConditionalIconSet
+    {
+        return $this->iconSet;
+    }
+
+    public function setIconSet(ConditionalIconSet $iconSet): static
+    {
+        $this->iconSet = $iconSet;
+
+        return $this;
+    }
+
     /**
      * Get hash code.
      *
@@ -327,10 +344,10 @@ public function getHashCode(): string
     {
         return md5(
             $this->conditionType
-            . $this->operatorType
-            . implode(';', $this->condition)
-            . $this->style->getHashCode()
-            . __CLASS__
+                . $this->operatorType
+                . implode(';', $this->condition)
+                . $this->style->getHashCode()
+                . __CLASS__
         );
     }
 
diff --git a/src/PhpSpreadsheet/Style/ConditionalFormatting/ConditionalFormatValueObject.php b/src/PhpSpreadsheet/Style/ConditionalFormatting/ConditionalFormatValueObject.php
index e6d1035f4e..d1dfb51593 100644
--- a/src/PhpSpreadsheet/Style/ConditionalFormatting/ConditionalFormatValueObject.php
+++ b/src/PhpSpreadsheet/Style/ConditionalFormatting/ConditionalFormatValueObject.php
@@ -10,6 +10,13 @@ class ConditionalFormatValueObject
 
     private ?string $cellFormula;
 
+    /**
+     * For icon sets, determines whether this threshold value uses the greater
+     * than or equal to operator. False indicates 'greater than' is used instead
+     * of 'greater than or equal to'.
+     */
+    private ?bool $greaterThanOrEqual = null;
+
     public function __construct(string $type, null|float|int|string $value = null, ?string $cellFormula = null)
     {
         $this->type = $type;
@@ -52,4 +59,16 @@ public function setCellFormula(?string $cellFormula): self
 
         return $this;
     }
+
+    public function getGreaterThanOrEqual(): ?bool
+    {
+        return $this->greaterThanOrEqual;
+    }
+
+    public function setGreaterThanOrEqual(?bool $greaterThanOrEqual): self
+    {
+        $this->greaterThanOrEqual = $greaterThanOrEqual;
+
+        return $this;
+    }
 }
diff --git a/src/PhpSpreadsheet/Style/ConditionalFormatting/ConditionalIconSet.php b/src/PhpSpreadsheet/Style/ConditionalFormatting/ConditionalIconSet.php
new file mode 100644
index 0000000000..b7c21d869e
--- /dev/null
+++ b/src/PhpSpreadsheet/Style/ConditionalFormatting/ConditionalIconSet.php
@@ -0,0 +1,96 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting;
+
+class ConditionalIconSet
+{
+    /** The icon set to display. */
+    private ?IconSetValues $iconSetType = null;
+
+    /**  If true, reverses the default order of the icons in this icon set. */
+    private ?bool $reverse = null;
+
+    /** Indicates whether to show the values of the cells on which this icon set is applied. */
+    private ?bool $showValue = null;
+
+    /**
+     * If true, indicates that the icon set is a custom icon set.
+     * If this value is "true", there MUST be the same number of cfIcon elements
+     * as cfvo elements.
+     * If this value is "false", there MUST be 0 cfIcon elements.
+     */
+    private ?bool $custom = null;
+
+    /** @var ConditionalFormatValueObject[] */
+    private array $cfvos = [];
+
+    public function getIconSetType(): ?IconSetValues
+    {
+        return $this->iconSetType;
+    }
+
+    public function setIconSetType(IconSetValues $type): self
+    {
+        $this->iconSetType = $type;
+
+        return $this;
+    }
+
+    public function getReverse(): ?bool
+    {
+        return $this->reverse;
+    }
+
+    public function setReverse(bool $reverse): self
+    {
+        $this->reverse = $reverse;
+
+        return $this;
+    }
+
+    public function getShowValue(): ?bool
+    {
+        return $this->showValue;
+    }
+
+    public function setShowValue(bool $showValue): self
+    {
+        $this->showValue = $showValue;
+
+        return $this;
+    }
+
+    public function getCustom(): ?bool
+    {
+        return $this->custom;
+    }
+
+    public function setCustom(bool $custom): self
+    {
+        $this->custom = $custom;
+
+        return $this;
+    }
+
+    /**
+     * Get the conditional format value objects.
+     *
+     * @return ConditionalFormatValueObject[]
+     */
+    public function getCfvos(): array
+    {
+        return $this->cfvos;
+    }
+
+    /**
+     * Set the conditional format value objects.
+     *
+     * @param ConditionalFormatValueObject[] $cfvos
+     */
+    public function setCfvos(array $cfvos): self
+    {
+        $this->cfvos = $cfvos;
+
+        return $this;
+    }
+}
diff --git a/src/PhpSpreadsheet/Style/ConditionalFormatting/IconSetValues.php b/src/PhpSpreadsheet/Style/ConditionalFormatting/IconSetValues.php
new file mode 100644
index 0000000000..c27d36e6ed
--- /dev/null
+++ b/src/PhpSpreadsheet/Style/ConditionalFormatting/IconSetValues.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting;
+
+enum IconSetValues: string
+{
+    case ThreeArrows = '3Arrows';
+    case ThreeArrowsGray = '3ArrowsGray';
+    case ThreeFlags = '3Flags';
+    case ThreeTrafficLights1 = '3TrafficLights1';
+    case ThreeTrafficLights2 = '3TrafficLights2';
+    case ThreeSigns = '3Signs';
+    case ThreeSymbols = '3Symbols';
+    case ThreeSymbols2 = '3Symbols2';
+    case FourArrows = '4Arrows';
+    case FourArrowsGray = '4ArrowsGray';
+    case FourRedToBlack = '4RedToBlack';
+    case FourRating = '4Rating';
+    case FourTrafficLights = '4TrafficLights';
+    case FiveArrows = '5Arrows';
+    case FiveArrowsGray = '5ArrowsGray';
+    case FiveRating = '5Rating';
+    case FiveQuarters = '5Quarters';
+    // The following icon sets are not implemented yet:
+    // case ThreeStars = "3Stars";
+    // case ThreeTriangles = "3Triangles";
+    // case FiveBoxes = "5Boxes";
+}
diff --git a/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php b/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php
index 9ffa49f526..799ef65586 100644
--- a/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php
+++ b/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php
@@ -16,6 +16,7 @@
 use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalColorScale;
 use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalDataBar;
 use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalFormattingRuleExtension;
+use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalIconSet;
 use PhpOffice\PhpSpreadsheet\Style\Font;
 use PhpOffice\PhpSpreadsheet\Worksheet\RowDimension;
 use PhpOffice\PhpSpreadsheet\Worksheet\SheetView;
@@ -863,6 +864,47 @@ private static function writeColorScaleElements(XMLWriter $objWriter, ?Condition
         }
     }
 
+    private function writeIconSetElements(XMLWriter $objWriter, ?ConditionalIconSet $iconSet): void
+    {
+        if ($iconSet === null) {
+            return;
+        }
+
+        $objWriter->startElement('iconSet');
+        if ($iconSet->getIconSetType() !== null) {
+            $objWriter->writeAttribute('iconSet', $iconSet->getIconSetType()->value);
+        }
+        foreach (
+            [
+                'reverse' => $iconSet->getReverse(),
+                'showValue' => $iconSet->getShowValue(),
+                'custom' => $iconSet->getCustom(),
+            ] as $attr => $value
+        ) {
+            self::writeAttributeIf($objWriter, $value !== null, $attr, $value ? '1' : '0');
+        }
+
+        foreach ($iconSet->getCfvos() as $cfvo) {
+            $objWriter->startElement('cfvo');
+            $objWriter->writeAttribute('type', $cfvo->getType());
+            self::writeAttributeIf(
+                $objWriter,
+                $cfvo->getValue() !== null,
+                'val',
+                (string) $cfvo->getValue(),
+            );
+            self::writeAttributeIf(
+                $objWriter,
+                $cfvo->getGreaterThanOrEqual() !== null,
+                'gte',
+                $cfvo->getGreaterThanOrEqual() ? '1' : '0',
+            );
+            $objWriter->endElement(); // end cfvo
+        }
+
+        $objWriter->endElement(); // end iconSet
+    }
+
     /**
      * Write ConditionalFormatting.
      */
@@ -897,6 +939,7 @@ private function writeConditionalFormatting(XMLWriter $objWriter, Phpspreadsheet
                     $objWriter,
                     ($conditional->getConditionType() !== Conditional::CONDITION_COLORSCALE
                         && $conditional->getConditionType() !== Conditional::CONDITION_DATABAR
+                        && $conditional->getConditionType() !== Conditional::CONDITION_ICONSET
                         && $conditional->getNoFormatSet() === false),
                     'dxfId',
                     (string) $this->getParentWriter()->getStylesConditionalHashTable()->getIndexForHashCode($conditional->getHashCode())
@@ -933,6 +976,8 @@ private function writeConditionalFormatting(XMLWriter $objWriter, Phpspreadsheet
                     self::writeTimePeriodCondElements($objWriter, $conditional, $topLeftCell);
                 } elseif ($conditional->getConditionType() === Conditional::CONDITION_COLORSCALE) {
                     self::writeColorScaleElements($objWriter, $conditional->getColorScale());
+                } elseif ($conditional->getConditionType() === Conditional::CONDITION_ICONSET) {
+                    self::writeIconSetElements($objWriter, $conditional->getIconSet());
                 } else {
                     self::writeOtherCondElements($objWriter, $conditional, $topLeftCell);
                 }
@@ -1566,8 +1611,8 @@ private function writeCellFormula(XMLWriter $objWriter, string $cellValue, Cell
             self::writeElementIf(
                 $objWriter,
                 $this->getParentWriter()->getOffice2003Compatibility() === false
-                && $this->getParentWriter()->getPreCalculateFormulas()
-                && $calculatedValue !== null,
+                    && $this->getParentWriter()->getPreCalculateFormulas()
+                    && $calculatedValue !== null,
                 'v',
                 (!is_array($calculatedValue) && !str_starts_with($calculatedValueString, '#'))
                     ? StringHelper::formatNumber($calculatedValueString) : '0'
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalIconSetTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalIconSetTest.php
new file mode 100644
index 0000000000..e3e77d0b40
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalIconSetTest.php
@@ -0,0 +1,87 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
+
+use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\IconSetValues;
+use PhpOffice\PhpSpreadsheetTests\Functional\AbstractFunctional;
+
+class ConditionalIconSetTest extends AbstractFunctional
+{
+    public function testIconSet(): void
+    {
+        $filename = 'tests/data/Reader/XLSX/conditionalFormattingIconSet.xlsx';
+        $reader = \PhpOffice\PhpSpreadsheet\IOFactory::createReader('Xlsx');
+        $spreadsheet = $reader->load($filename);
+        $reloadedSpreadsheet = $this->writeAndReload($spreadsheet, 'Xlsx');
+        $spreadsheet->disconnectWorksheets();
+        $worksheet = $reloadedSpreadsheet->getActiveSheet();
+
+        $columnIndex = 'A';
+        foreach (IconSetValues::cases() as $iconSetValue) {
+            // styles
+            $styles = $worksheet->getConditionalStyles("{$columnIndex}2:{$columnIndex}11");
+            self::assertCount(1, $styles);
+
+            // icon set
+            $iconSet = $styles[0]->getIconSet();
+            self::assertNotNull($iconSet);
+            self::assertSame($iconSetValue, $iconSet->getIconSetType() ?? IconSetValues::ThreeTrafficLights1);
+
+            ++$columnIndex;
+        }
+
+        // icon set attributes
+        $columnIndex = 'A';
+        foreach (
+            [
+                ['reverse' => false, 'showValue' => false],
+                ['reverse' => true, 'showValue' => false],
+                ['reverse' => false, 'showValue' => true],
+            ] as $expected
+        ) {
+            $styles = $worksheet->getConditionalStyles("{$columnIndex}2:{$columnIndex}11");
+            $iconSet = $styles[0]->getIconSet();
+            self::assertNotNull($iconSet);
+            self::assertSame($expected['reverse'], $iconSet->getReverse() ?? false);
+            self::assertSame($expected['showValue'], $iconSet->getShowValue() ?? true);
+            self::assertFalse($iconSet->getCustom() ?? false);
+
+            ++$columnIndex;
+        }
+
+        // cfvos
+        $columnIndex = 'A';
+        foreach (
+            [
+                [['percent', '0', true], ['percent', '33', false], ['percent', '67', true]],
+                [['percent', '0', true], ['num', '3', false], ['num', '7', true]],
+                [['percent', '0', true], ['formula', '10/3', false], ['formula', '10/2', true]],
+                [['percent', '0', true], ['percentile', '33', false], ['percentile', '67', true]],
+            ] as $expected
+        ) {
+            $styles = $worksheet->getConditionalStyles("{$columnIndex}2:{$columnIndex}11");
+            $iconSet = $styles[0]->getIconSet();
+            self::assertNotNull($iconSet);
+            $cfvos = $iconSet->getCfvos();
+            self::assertCount(count($expected), $cfvos);
+            foreach ($expected as $i => [$type, $value, $gte]) {
+                $cfvo = $cfvos[$i];
+                self::assertSame($type, $cfvo->getType());
+                self::assertSame($value, $cfvo->getValue());
+                self::assertSame($gte, $cfvo->getGreaterThanOrEqual() ?? true);
+                self::assertNull($cfvo->getCellFormula());
+            }
+
+            ++$columnIndex;
+        }
+
+        // unsupported icon sets
+        for ($columnIndex = 'R'; $columnIndex <= 'U'; ++$columnIndex) {
+            $styles = $worksheet->getConditionalStyles("{$columnIndex}2:{$columnIndex}11");
+            $iconSet = $styles[0]->getIconSet();
+            self::assertNull($iconSet);
+        }
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/ConditionalFormatIconSetTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/ConditionalFormatIconSetTest.php
new file mode 100644
index 0000000000..9d64b9b8a5
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/ConditionalFormatIconSetTest.php
@@ -0,0 +1,152 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
+
+use Generator;
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheet\Style\Conditional;
+use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalFormatValueObject;
+use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\ConditionalIconSet;
+use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\IconSetValues;
+use PhpOffice\PhpSpreadsheet\Writer\Xlsx;
+use PhpOffice\PhpSpreadsheetTests\Functional\AbstractFunctional;
+use PHPUnit\Framework\Attributes\DataProvider;
+
+class ConditionalFormatIconSetTest extends AbstractFunctional
+{
+    private const COORDINATE = 'A1:A3';
+
+    #[DataProvider('iconSetsProvider')]
+    public function testWriteIconSets(
+        string $expected,
+        ?IconSetValues $type,
+        ?bool $reverse = null,
+        ?bool $showValue = null,
+        ?bool $custom = null,
+    ): void {
+        $condition = new Conditional();
+        $condition->setConditionType(Conditional::CONDITION_ICONSET);
+        $iconSet = $condition->setIconSet(new ConditionalIconSet())
+            ->getIconSet();
+        self::assertNotNull($iconSet);
+        if ($type !== null) {
+            $iconSet->setIconSetType($type);
+        }
+        $iconSet->setCfvos([
+            new ConditionalFormatValueObject('percent', 0),
+            new ConditionalFormatValueObject('percent', 33),
+            new ConditionalFormatValueObject('percent', 67),
+        ]);
+        if ($reverse !== null) {
+            $iconSet->setReverse($reverse);
+        }
+        if ($showValue !== null) {
+            $iconSet->setShowValue($showValue);
+        }
+        if ($custom !== null) {
+            $iconSet->setCustom($custom);
+        }
+
+        $spreadsheet = new Spreadsheet();
+        $worksheet = $spreadsheet->getActiveSheet();
+        $worksheet->setConditionalStyles(self::COORDINATE, [$condition]);
+
+        $writer = new Xlsx($spreadsheet);
+        $writerWorksheet = new Xlsx\Worksheet($writer);
+        $data = $writerWorksheet->writeWorksheet($worksheet, []);
+
+        $expected = preg_replace(['/^\s+/m', "/\n/"], '', $expected);
+        self::assertIsString($expected);
+        self::assertStringContainsString($expected, $data);
+    }
+
+    public static function iconSetsProvider(): Generator
+    {
+        $coordinate = self::COORDINATE;
+        $cfvos = <<<XML
+            <cfvo type="percent" val="0"/>
+            <cfvo type="percent" val="33"/>
+            <cfvo type="percent" val="67"/>
+            XML;
+        foreach (IconSetValues::cases() as $type) {
+            yield $type->name => [
+                <<<XML
+                    <conditionalFormatting sqref="{$coordinate}">
+                        <cfRule type="iconSet" priority="1">
+                            <iconSet iconSet="{$type->value}">
+                                {$cfvos}
+                            </iconSet>
+                        </cfRule>
+                    </conditionalFormatting>
+                    XML,
+                $type,
+            ];
+        }
+
+        yield 'null' => [
+            <<<XML
+                <conditionalFormatting sqref="{$coordinate}">
+                    <cfRule type="iconSet" priority="1">
+                        <iconSet>
+                            {$cfvos}
+                        </iconSet>
+                    </cfRule>
+                </conditionalFormatting>
+                XML,
+            null,
+        ];
+
+        foreach ([1, 0] as $reverse) {
+            yield "null/reverse=$reverse" => [
+                <<<XML
+                    <conditionalFormatting sqref="{$coordinate}">
+                        <cfRule type="iconSet" priority="1">
+                            <iconSet reverse="$reverse">
+                                {$cfvos}
+                            </iconSet>
+                        </cfRule>
+                    </conditionalFormatting>
+                    XML,
+                null,
+                $reverse === 1,
+            ];
+        }
+
+        foreach ([1, 0] as $showValue) {
+            yield "null/showValue=$showValue" => [
+                <<<XML
+                    <conditionalFormatting sqref="{$coordinate}">
+                        <cfRule type="iconSet" priority="1">
+                            <iconSet showValue="$showValue">
+                                {$cfvos}
+                            </iconSet>
+                        </cfRule>
+                    </conditionalFormatting>
+                    XML,
+                null,
+                null,
+                $showValue === 1,
+            ];
+        }
+
+        foreach ([1, 0] as $custom) {
+            yield "null/custom=$custom" => [
+                <<<XML
+                    <conditionalFormatting sqref="{$coordinate}">
+                        <cfRule type="iconSet" priority="1">
+                            <iconSet custom="$custom">
+                                {$cfvos}
+                            </iconSet>
+                        </cfRule>
+                    </conditionalFormatting>
+                    XML,
+                null,
+                null,
+                null,
+                $custom === 1,
+            ];
+        }
+    }
+}
diff --git a/tests/data/Reader/XLSX/conditionalFormattingIconSet.xlsx b/tests/data/Reader/XLSX/conditionalFormattingIconSet.xlsx
new file mode 100644
index 0000000000..e731b973f8
Binary files /dev/null and b/tests/data/Reader/XLSX/conditionalFormattingIconSet.xlsx differ