diff --git a/.github/scripts/package.json b/.github/scripts/package.json
index 2c2e5207d..26ab7802a 100644
--- a/.github/scripts/package.json
+++ b/.github/scripts/package.json
@@ -16,6 +16,6 @@
     "devDependencies": {
         "@octokit/rest": "^19.0.0",
         "mocha": "^10.0.0",
-        "sinon": "^18.0.0"
+        "sinon": "^21.0.0"
     }
 }
\ No newline at end of file
diff --git a/package.json b/package.json
index 7816f9851..7b8edd63e 100644
--- a/package.json
+++ b/package.json
@@ -75,7 +75,7 @@
     "p-queue": "^8.1.0",
     "pack-n-play": "^3.0.1",
     "proxyquire": "^2.1.3",
-    "sinon": "^20.0.0",
+    "sinon": "^21.0.0",
     "ts-loader": "^9.5.2",
     "typescript": "^5.8.3",
     "webpack-cli": "^6.0.1"
diff --git a/samples/package.json b/samples/package.json
index f4033a807..622d0a9e7 100644
--- a/samples/package.json
+++ b/samples/package.json
@@ -15,7 +15,7 @@
   },
   "dependencies": {
     "@google-cloud/datastore": "^10.0.1",
-    "sinon": "^18.0.0"
+    "sinon": "^21.0.0"
   },
   "devDependencies": {
     "chai": "^4.2.0",