diff --git a/BUILDING.md b/BUILDING.md
index 891e8aea40..5670aeeaf2 100644
--- a/BUILDING.md
+++ b/BUILDING.md
@@ -13,8 +13,8 @@ cd <path-to-agi-source>
 bazel build pkg
 ```
 
-> :warning: We currently use NDK r21 to have access to the unified Khronos
-> validation layer. Bazel 2.0.0 has no official support for r21, so **the
+> :warning: We currently use NDK r21d to have access to the unified Khronos
+> validation layer. Bazel 2.0.0 has no official support for r21d, so **the
 > following build warning is expected and can be ignored:**
 >
 > ```
@@ -84,7 +84,7 @@ tools\bin\sdkmanager.bat platform-tools
 ```
 
 Unzip the
-[Android NDK **r21**](https://dl.google.com/android/repository/android-ndk-r21-windows-x86_64.zip)
+[Android NDK **r21d**](https://dl.google.com/android/repository/android-ndk-r21d-windows-x86_64.zip)
 into a directory of your choosing, and set the `ANDROID_NDK_HOME` environment
 variable to point to this directory.
 
@@ -145,7 +145,7 @@ tools/bin/sdkmanager platform-tools
 ```
 
 Unzip the
-[Android NDK **r21**](https://dl.google.com/android/repository/android-ndk-r21-darwin-x86_64.zip)
+[Android NDK **r21d**](https://dl.google.com/android/repository/android-ndk-r21d-darwin-x86_64.zip)
 into a directory of your choosing, and set the `ANDROID_NDK_HOME` environment
 variable to point to this directory:
 
@@ -219,7 +219,7 @@ tools/bin/sdkmanager platform-tools
 ```
 
 Unzip the
-[Android NDK **r21**](https://dl.google.com/android/repository/android-ndk-r21-linux-x86_64.zip)
+[Android NDK **r21d**](https://dl.google.com/android/repository/android-ndk-r21d-linux-x86_64.zip)
 into a directory of your choosing, and set the `ANDROID_NDK_HOME` environment
 variable to point to this directory:
 
diff --git a/kokoro/linux/build.sh b/kokoro/linux/build.sh
index 7f5a023721..a2d318bd1b 100755
--- a/kokoro/linux/build.sh
+++ b/kokoro/linux/build.sh
@@ -20,9 +20,9 @@ BUILD_ROOT=$PWD
 SRC=$PWD/github/agi/
 
 # Get the Android NDK
-curl -L -k -O -s https://dl.google.com/android/repository/android-ndk-r21-linux-x86_64.zip
-unzip -q android-ndk-r21-linux-x86_64.zip
-export ANDROID_NDK_HOME=$PWD/android-ndk-r21
+curl -L -k -O -s https://dl.google.com/android/repository/android-ndk-r21d-linux-x86_64.zip
+unzip -q android-ndk-r21d-linux-x86_64.zip
+export ANDROID_NDK_HOME=$PWD/android-ndk-r21d
 
 # Get recent build tools
 # Note: the SDK manager needs Java8, call it before switching to Java11
diff --git a/kokoro/macos/build.sh b/kokoro/macos/build.sh
index e026fc1f2b..a5ae883e6a 100755
--- a/kokoro/macos/build.sh
+++ b/kokoro/macos/build.sh
@@ -25,10 +25,10 @@ curl -L -k -O -s https://dl.google.com/android/repository/tools_r25.2.3-macosx.z
 mkdir android
 unzip -q tools_r25.2.3-macosx.zip -d android
 echo y | ./android/tools/bin/sdkmanager build-tools\;29.0.2 platforms\;android-26
-curl -L -k -O -s https://dl.google.com/android/repository/android-ndk-r21-darwin-x86_64.zip
-unzip -q android-ndk-r21-darwin-x86_64.zip -d android
+curl -L -k -O -s https://dl.google.com/android/repository/android-ndk-r21d-darwin-x86_64.zip
+unzip -q android-ndk-r21d-darwin-x86_64.zip -d android
 export ANDROID_HOME=$PWD/android
-export ANDROID_NDK_HOME=$PWD/android/android-ndk-r21
+export ANDROID_NDK_HOME=$PWD/android/android-ndk-r21d
 
 # Get Zulu JDK11 from bazel, see https://mirror.bazel.build/openjdk/index.html
 ZULU_JDK="zulu11.31.11-ca-jdk11.0.3"
diff --git a/kokoro/windows/build.bat b/kokoro/windows/build.bat
index d7a6f0f081..4ca130b3f3 100644
--- a/kokoro/windows/build.bat
+++ b/kokoro/windows/build.bat
@@ -34,9 +34,9 @@ REM Note: the SDK manager needs Java8, call it before switching to Java11
 setlocal
 call %ANDROID_HOME%\tools\bin\sdkmanager.bat platforms;android-26 build-tools;29.0.2
 endlocal
-wget -q https://dl.google.com/android/repository/android-ndk-r21-windows-x86_64.zip
-unzip -q android-ndk-r21-windows-x86_64.zip
-set ANDROID_NDK_HOME=%CD%\android-ndk-r21
+wget -q https://dl.google.com/android/repository/android-ndk-r21d-windows-x86_64.zip
+unzip -q android-ndk-r21d-windows-x86_64.zip
+set ANDROID_NDK_HOME=%CD%\android-ndk-r21d
 
 REM Install WiX Toolset.
 wget -q https://github.com/wixtoolset/wix3/releases/download/wix311rtm/wix311-binaries.zip
diff --git a/tools/build/rules/android.bzl b/tools/build/rules/android.bzl
index 311e54832b..e20ca836a5 100644
--- a/tools/build/rules/android.bzl
+++ b/tools/build/rules/android.bzl
@@ -139,7 +139,7 @@ ndk_vk_validation_layer = repository_rule(
 # Enforce NDK version by checking $ANDROID_NDK_HOME/source.properties
 def _ndk_version_check(repository_ctx):
     # This should be updated in sync with BUILDING.md documentation
-    expectedVersion = "21.0.6113669"
+    expectedVersion = "21.3.6528147"
 
     # Extract NDK version string from $ANDROID_NDK_HOME/source.properties,
     # which has the following format: