diff --git a/.github/workflows/dep_build_v2.yml b/.github/workflows/dep_build_v2.yml
index 7fcc9169..53ee7cbd 100644
--- a/.github/workflows/dep_build_v2.yml
+++ b/.github/workflows/dep_build_v2.yml
@@ -16,7 +16,7 @@ jobs:
       matrix:
         java_version: ['8', '17', '21', '24']
         # Versions need to align with ones in 'main.yml' workflow
-        kotlin_version: ['2.0.21', '2.1.21', '2.2.10']
+        kotlin_version: ['2.1.21', '2.2.10']
     env:
       JAVA_OPTS: "-XX:+TieredCompilation -XX:TieredStopAtLevel=1"
     steps:
diff --git a/.github/workflows/dep_build_v3.yml b/.github/workflows/dep_build_v3.yml
index e6b821a9..41cff610 100644
--- a/.github/workflows/dep_build_v3.yml
+++ b/.github/workflows/dep_build_v3.yml
@@ -14,7 +14,7 @@ jobs:
       matrix:
         java_version: ['17', '21', '24']
         # Versions need to align with ones in 'main.yml' workflow
-        kotlin_version: ['2.0.21', '2.1.21', '2.2.10']
+        kotlin_version: ['2.1.21', '2.2.10']
     env:
       JAVA_OPTS: "-XX:+TieredCompilation -XX:TieredStopAtLevel=1"
     steps:
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index e3a73b94..baed12ec 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -21,10 +21,10 @@ jobs:
       max-parallel: 5
       matrix:
         java_version: ['8', '11', '17', '21', '24']
-        kotlin_version: ['2.0.21', '2.1.21', '2.2.10']
+        kotlin_version: ['2.1.21', '2.2.10']
         include:
           - java_version: '8'
-            kotlin_version: '2.0.21'
+            kotlin_version: '2.1.21'
             release_build: 'R'
     env:
       JAVA_OPTS: "-XX:+TieredCompilation -XX:TieredStopAtLevel=1"
diff --git a/README.md b/README.md
index c23b619a..f2c58110 100644
--- a/README.md
+++ b/README.md
@@ -111,10 +111,10 @@ println(arrayNode.toString()) // ["foo",true,1,1.0,"YmFy"]
 Different `kotlin-core` versions are supported by different Jackson Kotlin module minor versions.
 Here is an incomplete list of supported versions:
 
+* Jackson 2.21.x: Kotlin-core 2.1 - 2.2
 * Jackson 2.20.x: Kotlin-core 2.0 - 2.2
 * Jackson 2.19.x: Kotlin-core 1.9 - 2.1
 * Jackson 2.18.x: Kotlin-core 1.8 - 2.1
-* Jackson 2.17.x: Kotlin-core 1.7 - 2.0
 
 Please note that the versions supported by 2.17 are tentative and may change depending on the release date.
 
diff --git a/pom.xml b/pom.xml
index 5419900c..96b71df5 100644
--- a/pom.xml
+++ b/pom.xml
@@ -62,7 +62,7 @@
         <javac.src.version>1.8</javac.src.version>
         <javac.target.version>1.8</javac.target.version>
 
-        <version.kotlin>2.0.21</version.kotlin>
+        <version.kotlin>2.1.21</version.kotlin>
 
         <!-- Generate PackageVersion.java into this directory. -->
         <packageVersion.dir>com/fasterxml/jackson/module/kotlin</packageVersion.dir>
diff --git a/release-notes/CREDITS-2.x b/release-notes/CREDITS-2.x
index 9af9b8ef..6ca59364 100644
--- a/release-notes/CREDITS-2.x
+++ b/release-notes/CREDITS-2.x
@@ -15,7 +15,12 @@ Authors:
 
 Contributors:
 
-# 2.20.0 (not yet released)
+# 2.21.0 (not yet released)
+
+WrongWrong (@k163377)
+* #1039: Update settings for 2.20
+
+# 2.20.0 (28-Aug-2025)
 
 WrongWrong (@k163377)
 * #1025: Deprecate MissingKotlinParameterException and replace with new exception
diff --git a/release-notes/VERSION-2.x b/release-notes/VERSION-2.x
index dd49c395..ee3718fe 100644
--- a/release-notes/VERSION-2.x
+++ b/release-notes/VERSION-2.x
@@ -18,7 +18,7 @@ Co-maintainers:
 
 2.21.0 (not yet released)
 
-No changes since 2.20
+#1039: Kotlin has been upgraded to 2.1.x.
 
 2.20.0 (28-Aug-2025)