diff --git a/src/rules/no-invalid-properties.js b/src/rules/no-invalid-properties.js
index 104d236b..cc7c0810 100644
--- a/src/rules/no-invalid-properties.js
+++ b/src/rules/no-invalid-properties.js
@@ -37,7 +37,7 @@ function getVarFallbackList(value) {
 
 	while (true) {
 		const match = currentValue.match(
-			/var\(\s*(--[^,\s)]+)\s*(?:,\s*(.+))?\)/u,
+			/var\(\s*(--[^,\s)]+)\s*(?:,\s*(.+))?\)/iu,
 		);
 
 		if (!match) {
@@ -54,7 +54,7 @@ function getVarFallbackList(value) {
 		}
 
 		// If fallback is not another var(), we're done
-		if (!fallback.includes("var(")) {
+		if (!fallback.toLowerCase().includes("var(")) {
 			list.push(fallback);
 			break;
 		}
@@ -129,7 +129,7 @@ export default {
 				replacements.push(new Map());
 			},
 
-			"Function[name=var]"(node) {
+			"Function[name=/^var$/i]"(node) {
 				const map = replacements.at(-1);
 				if (!map) {
 					return;
@@ -166,7 +166,10 @@ export default {
 					// When `var()` is used, we store all the values to `valueList` with the replacement of `var()` with there values or fallback values
 					for (const child of valueNodes) {
 						// If value is a function starts with `var()`
-						if (child.type === "Function" && child.name === "var") {
+						if (
+							child.type === "Function" &&
+							child.name.toLowerCase() === "var"
+						) {
 							const varValue = vars.get(child.children[0].name);
 
 							// If the variable is found, use its value, otherwise check for fallback values
diff --git a/tests/rules/no-invalid-properties.test.js b/tests/rules/no-invalid-properties.test.js
index d8768749..fa5babc3 100644
--- a/tests/rules/no-invalid-properties.test.js
+++ b/tests/rules/no-invalid-properties.test.js
@@ -55,6 +55,29 @@ ruleTester.run("no-invalid-properties", rule, {
 		":root { --my-color: red; }\na { color: var(--my-color, var(--fallback-color, var(--foo, var(--bar)))) }",
 		":root { --my-color: red; }\na { color: var(--my-color, var(--fallback-color, var(--foo, var(--bar, blue)))) }",
 		":root { --color: red }\na { border-top: 1px var(--style, var(--fallback, solid)) var(--color, blue); }",
+		"a { color: VAR(--my-color, red) }",
+		":root { --my-heading: 3rem; }\na { color: vAr(--my-color, red) }",
+		":root { --my-heading: 3rem; --foo: red }\na { color: VAR(--my-color, VAR(--foo, blue)) }",
+		":root { --my-heading: 3rem; }\na { color: VAR(--my-color, vAr(--foo, blue)) }",
+		"a { color: vAR(--my-color, VaR(--foo, VAR(--bar, blue))) }",
+		":root { --my-color: red; }\na { color: Var(--my-color, blue) }",
+		":root { --my-fallback: red; }\na { color: var(--my-color, VAR(--my-fallback)) }",
+		":root { --my-fallback: red; }\na { color: VAR(--my-color, var(--my-fallback, blue)) }",
+		":root { --foo: red; }\na { color: vAr(--my-color, VAR(--my-fallback, VaR(--foo))) }",
+		"a { color: VAR(--my-color, vAr(--my-fallback, VAR(--foo, blue))) }",
+		":root { --my-color: red; }\na { color: Var(--my-color, VAR(--fallback-color)) }",
+		":root { --my-color: red; --fallback-color: blue; }\na { color: VAR(--my-color, var(--fallback-color)) }",
+		":root { --my-color: red; }\na { color: var(--my-color, VaR(--fallback-color, blue)) }",
+		":root { --my-color: red; }\na { color: VAR(--my-color, vAr(--fallback-color, VAR(--foo))) }",
+		":root { --my-color: red; }\na { color: vAr(--my-color, VAR(--fallback-color, var(--foo, blue))) }",
+		":root { --my-color: red; }\na { color: VAR(--my-color, vAr(--fallback-color, VAR(--foo, var(--bar)))) }",
+		":root { --my-color: red; }\na { color: vAr(--my-color, VAR(--fallback-color, var(--foo, VaR(--bar, blue)))) }",
+		":root { --color: red }\na { border-top: 1px VAR(--style, vAr(--fallback, solid)) VaR(--color, blue); }",
+		":root { --MY-COLOR: red; }\na { color: var(--MY-COLOR) }",
+		":root { --my-color: red; }\na { color: var(--MY-COLOR, red) }",
+		":root { --MY-COLOR: red; }\na { color: var(--my-color, blue) }",
+		":root { --FALLBACK-COLOR: blue; }\na { color: var(--MY-COLOR, var(--FALLBACK-COLOR)) }",
+		":root { --fallback-color: blue; }\na { color: VAR(--MY-COLOR, VaR(--fallback-color)) }",
 		{
 			code: "a { my-custom-color: red; }",
 			languageOptions: {
@@ -69,6 +92,10 @@ ruleTester.run("no-invalid-properties", rule, {
 			code: "a { color: var(--my-color); }",
 			options: [{ allowUnknownVariables: true }],
 		},
+		{
+			code: "a { color: VAR(--my-color); }",
+			options: [{ allowUnknownVariables: true }],
+		},
 		{
 			code: "a { --my-color: red; color: var(--my-color); background-color: var(--unknown-var); }",
 			options: [{ allowUnknownVariables: true }],
@@ -77,6 +104,10 @@ ruleTester.run("no-invalid-properties", rule, {
 			code: ":root { --color: red }\na { border-top: 1px var(--style, var(--fallback)) var(--color, blue); }",
 			options: [{ allowUnknownVariables: true }],
 		},
+		{
+			code: ":root { --color: red }\na { border-top: 1px VAR(--style, VAR(--fallback)) VAR(--color, blue); }",
+			options: [{ allowUnknownVariables: true }],
+		},
 
 		/*
 		 * CSSTree doesn't currently support custom functions properly, so leaving
@@ -295,6 +326,36 @@ ruleTester.run("no-invalid-properties", rule, {
 				},
 			],
 		},
+		{
+			code: "a { color: var(--MY-COLOR); }",
+			errors: [
+				{
+					messageId: "unknownVar",
+					data: {
+						var: "--MY-COLOR",
+					},
+					line: 1,
+					column: 16,
+					endLine: 1,
+					endColumn: 26,
+				},
+			],
+		},
+		{
+			code: "a { --my-color: red; color: var(--MY-COLOR); }",
+			errors: [
+				{
+					messageId: "unknownVar",
+					data: {
+						var: "--MY-COLOR",
+					},
+					line: 1,
+					column: 33,
+					endLine: 1,
+					endColumn: 43,
+				},
+			],
+		},
 		{
 			code: "a { .foo { color: var(--undefined-var); } }",
 			errors: [
@@ -310,6 +371,21 @@ ruleTester.run("no-invalid-properties", rule, {
 				},
 			],
 		},
+		{
+			code: "a { color: var(--MY-COLOR, var(--FALLBACK-COLOR)); }",
+			errors: [
+				{
+					messageId: "unknownVar",
+					data: {
+						var: "--MY-COLOR",
+					},
+					line: 1,
+					column: 16,
+					endLine: 1,
+					endColumn: 26,
+				},
+			],
+		},
 		{
 			code: "a { --my-color: 10px; color: var(--my-color); }",
 			errors: [
@@ -592,5 +668,134 @@ ruleTester.run("no-invalid-properties", rule, {
 				},
 			],
 		},
+		{
+			code: "a { color: VAR(--my-color); }",
+			errors: [
+				{
+					messageId: "unknownVar",
+					data: {
+						var: "--my-color",
+					},
+					line: 1,
+					column: 16,
+					endLine: 1,
+					endColumn: 26,
+				},
+			],
+		},
+		{
+			code: "a { border-top: 1px vAr(--style, solid) VaR(--color); }",
+			errors: [
+				{
+					messageId: "unknownVar",
+					data: {
+						var: "--color",
+					},
+					line: 1,
+					column: 45,
+					endLine: 1,
+					endColumn: 52,
+				},
+			],
+		},
+		{
+			code: ":root { --style: foo }\na { border-top: 1px VAR(--style) VAR(--color, red); }",
+			errors: [
+				{
+					messageId: "invalidPropertyValue",
+					data: {
+						property: "border-top",
+						value: "foo",
+						expected: "<line-width> || <line-style> || <color>",
+					},
+					line: 2,
+					column: 21,
+					endLine: 2,
+					endColumn: 33,
+				},
+			],
+		},
+		{
+			code: ":root { --style: foo }\na { border-top: 1px VAR(--style, solid) VAR(--color, red); }",
+			errors: [
+				{
+					messageId: "invalidPropertyValue",
+					data: {
+						property: "border-top",
+						value: "foo",
+						expected: "<line-width> || <line-style> || <color>",
+					},
+					line: 2,
+					column: 21,
+					endLine: 2,
+					endColumn: 40,
+				},
+			],
+		},
+		{
+			code: ":root { --color: foo }\na { border-top: 1px VAR(--style, VAR(--fallback, solid)) VAR(--color); }",
+			errors: [
+				{
+					messageId: "invalidPropertyValue",
+					data: {
+						property: "border-top",
+						value: "foo",
+						expected: "<line-width> || <line-style> || <color>",
+					},
+					line: 2,
+					column: 58,
+					endLine: 2,
+					endColumn: 70,
+				},
+			],
+		},
+		{
+			code: ":root { --color: foo }\na { border-top: 1px VAR(--style, VAR(--fallback)) VAR(--color); }",
+			options: [{ allowUnknownVariables: true }],
+			errors: [
+				{
+					messageId: "invalidPropertyValue",
+					data: {
+						property: "border-top",
+						value: "foo",
+						expected: "<line-width> || <line-style> || <color>",
+					},
+					line: 2,
+					column: 51,
+					endLine: 2,
+					endColumn: 63,
+				},
+			],
+		},
+		{
+			code: ":root { --color: foo }\na { border-top: 1px VAR(--style, VAR(--fallback)) VAR(--color); }",
+			errors: [
+				{
+					messageId: "unknownVar",
+					data: {
+						var: "--style",
+					},
+					line: 2,
+					column: 25,
+					endLine: 2,
+					endColumn: 32,
+				},
+			],
+		},
+		{
+			code: ":root { --color: red }\na { colorr: VAR(--color, blue); }",
+			errors: [
+				{
+					messageId: "unknownProperty",
+					data: {
+						property: "colorr",
+					},
+					line: 2,
+					column: 5,
+					endLine: 2,
+					endColumn: 11,
+				},
+			],
+		},
 	],
 });