diff --git a/.github/workflows/publish-nuget-Package.yml b/.github/workflows/publish-nuget-Package.yml
index 88f9dec..987e9b7 100644
--- a/.github/workflows/publish-nuget-Package.yml
+++ b/.github/workflows/publish-nuget-Package.yml
@@ -1,7 +1,7 @@
 name: Publish Nuget Package
 
 env:
-    NUGET_PACKAGE_NAME_VERSION: "GmailHelper.1.9.20.nupkg"
+    NUGET_PACKAGE_NAME_VERSION: "GmailHelper.1.9.21.nupkg"
 
 on:
   workflow_dispatch:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 52dbf41..c4b41a2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,10 @@ All notable changes to this project documented here.
 
 ## [Released]
 
+## [1.9.21](https://www.nuget.org/packages/GmailHelper/1.9.21) - 2024-02-10
+### Changed
+- Gmail API dependency update ('1.64.0.3287' -> '1.65.0.3287').
+
 ## [1.9.20](https://www.nuget.org/packages/GmailHelper/1.9.20) - 2024-01-11
 ### Changed
 - Gmail API dependency update ('1.64.0.3231' -> '1.64.0.3287').
diff --git a/GmailAPIHelper.NET.Tests/GmailAPIHelper.NET.Tests.csproj b/GmailAPIHelper.NET.Tests/GmailAPIHelper.NET.Tests.csproj
index e356293..93047d1 100644
--- a/GmailAPIHelper.NET.Tests/GmailAPIHelper.NET.Tests.csproj
+++ b/GmailAPIHelper.NET.Tests/GmailAPIHelper.NET.Tests.csproj
@@ -41,23 +41,23 @@
     <WarningLevel>4</WarningLevel>
   </PropertyGroup>
   <ItemGroup>
-    <Reference Include="Google.Apis, Version=1.64.0.0, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
-      <HintPath>..\packages\Google.Apis.1.64.0\lib\net45\Google.Apis.dll</HintPath>
+    <Reference Include="Google.Apis, Version=1.65.0.0, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+      <HintPath>..\packages\Google.Apis.1.65.0\lib\net45\Google.Apis.dll</HintPath>
     </Reference>
-    <Reference Include="Google.Apis.Auth, Version=1.64.0.0, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
-      <HintPath>..\packages\Google.Apis.Auth.1.64.0\lib\net461\Google.Apis.Auth.dll</HintPath>
+    <Reference Include="Google.Apis.Auth, Version=1.65.0.0, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+      <HintPath>..\packages\Google.Apis.Auth.1.65.0\lib\net461\Google.Apis.Auth.dll</HintPath>
     </Reference>
-    <Reference Include="Google.Apis.Auth.PlatformServices, Version=1.64.0.0, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
-      <HintPath>..\packages\Google.Apis.Auth.1.64.0\lib\net461\Google.Apis.Auth.PlatformServices.dll</HintPath>
+    <Reference Include="Google.Apis.Auth.PlatformServices, Version=1.65.0.0, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+      <HintPath>..\packages\Google.Apis.Auth.1.65.0\lib\net461\Google.Apis.Auth.PlatformServices.dll</HintPath>
     </Reference>
-    <Reference Include="Google.Apis.Core, Version=1.64.0.0, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
-      <HintPath>..\packages\Google.Apis.Core.1.64.0\lib\net45\Google.Apis.Core.dll</HintPath>
+    <Reference Include="Google.Apis.Core, Version=1.65.0.0, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+      <HintPath>..\packages\Google.Apis.Core.1.65.0\lib\net45\Google.Apis.Core.dll</HintPath>
     </Reference>
-    <Reference Include="Google.Apis.Gmail.v1, Version=1.64.0.3287, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
-      <HintPath>..\packages\Google.Apis.Gmail.v1.1.64.0.3287\lib\net45\Google.Apis.Gmail.v1.dll</HintPath>
+    <Reference Include="Google.Apis.Gmail.v1, Version=1.65.0.3287, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+      <HintPath>..\packages\Google.Apis.Gmail.v1.1.65.0.3287\lib\net45\Google.Apis.Gmail.v1.dll</HintPath>
     </Reference>
-    <Reference Include="Google.Apis.PlatformServices, Version=1.64.0.0, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
-      <HintPath>..\packages\Google.Apis.1.64.0\lib\net45\Google.Apis.PlatformServices.dll</HintPath>
+    <Reference Include="Google.Apis.PlatformServices, Version=1.65.0.0, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+      <HintPath>..\packages\Google.Apis.1.65.0\lib\net45\Google.Apis.PlatformServices.dll</HintPath>
     </Reference>
     <Reference Include="Microsoft.VisualStudio.TestPlatform.TestFramework, Version=14.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
       <HintPath>..\packages\MSTest.TestFramework.2.2.8\lib\net45\Microsoft.VisualStudio.TestPlatform.TestFramework.dll</HintPath>
diff --git a/GmailAPIHelper.NET.Tests/packages.config b/GmailAPIHelper.NET.Tests/packages.config
index bbf26de..292d5a1 100644
--- a/GmailAPIHelper.NET.Tests/packages.config
+++ b/GmailAPIHelper.NET.Tests/packages.config
@@ -1,9 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="Google.Apis" version="1.64.0" targetFramework="net461" />
-  <package id="Google.Apis.Auth" version="1.64.0" targetFramework="net461" />
-  <package id="Google.Apis.Core" version="1.64.0" targetFramework="net461" />
-  <package id="Google.Apis.Gmail.v1" version="1.64.0.3287" targetFramework="net461" />
+  <package id="Google.Apis" version="1.65.0" targetFramework="net461" />
+  <package id="Google.Apis.Auth" version="1.65.0" targetFramework="net461" />
+  <package id="Google.Apis.Core" version="1.65.0" targetFramework="net461" />
+  <package id="Google.Apis.Gmail.v1" version="1.65.0.3287" targetFramework="net461" />
   <package id="MimeKitLite" version="4.3.0" targetFramework="net461" />
   <package id="MSTest.TestAdapter" version="2.2.8" targetFramework="net461" />
   <package id="MSTest.TestFramework" version="2.2.8" targetFramework="net461" />
diff --git a/GmailAPIHelper/GmailAPIHelper.csproj b/GmailAPIHelper/GmailAPIHelper.csproj
index a39b70e..90de553 100644
--- a/GmailAPIHelper/GmailAPIHelper.csproj
+++ b/GmailAPIHelper/GmailAPIHelper.csproj
@@ -30,12 +30,12 @@ Solution Version:
     <PackageId>GmailHelper</PackageId>
     <RepositoryType>git</RepositoryType>
     <PackageLicenseFile>LICENSE</PackageLicenseFile>
-    <PackageReleaseNotes>1. Gmail API dependency update ('1.64.0.3231' -&gt; '1.64.0.3287').</PackageReleaseNotes>
-    <Version>1.9.20</Version>
+    <PackageReleaseNotes>1. Gmail API dependency update ('1.64.0.3287' -&gt; '1.65.0.3287').</PackageReleaseNotes>
+    <Version>1.9.21</Version>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Google.Apis.Gmail.v1" Version="1.64.0.3287" />
+    <PackageReference Include="Google.Apis.Gmail.v1" Version="1.65.0.3287" />
     <PackageReference Include="MimeKitLite" Version="4.3.0" />
   </ItemGroup>