diff --git a/src/Microsoft.ML.Tokenizers/Model/TiktokenTokenizer.cs b/src/Microsoft.ML.Tokenizers/Model/TiktokenTokenizer.cs
index b322be3a09..fdccf8facf 100644
--- a/src/Microsoft.ML.Tokenizers/Model/TiktokenTokenizer.cs
+++ b/src/Microsoft.ML.Tokenizers/Model/TiktokenTokenizer.cs
@@ -1044,6 +1044,7 @@ private static readonly (string Prefix, ModelEncoding Encoding)[] _modelPrefixTo
                                                                 ( "o4-mini-", ModelEncoding.O200kBase ),  // e.g. o4-mini
 
                                                                 // chat
+                                                                ( "gpt-5.2-", ModelEncoding.O200kBase ),
                                                                 ( "gpt-5.1-", ModelEncoding.O200kBase ),
                                                                 ( "gpt-5-", ModelEncoding.O200kBase ),
                                                                 ( "gpt-4.1-", ModelEncoding.O200kBase ),   // e.g., gpt-4.1-mini
@@ -1072,6 +1073,7 @@ private static readonly (string Prefix, ModelEncoding Encoding)[] _modelPrefixTo
                                                                 { "o4-mini", ModelEncoding.O200kBase },
 
                                                                 // chat
+                                                                { "gpt-5.2", ModelEncoding.O200kBase },
                                                                 { "gpt-5.1", ModelEncoding.O200kBase },
                                                                 { "gpt-5", ModelEncoding.O200kBase },
                                                                 { "gpt-4.1", ModelEncoding.O200kBase },
diff --git a/test/Microsoft.ML.Tokenizers.Tests/TiktokenTests.cs b/test/Microsoft.ML.Tokenizers.Tests/TiktokenTests.cs
index b77f981aec..c7c1e342d8 100644
--- a/test/Microsoft.ML.Tokenizers.Tests/TiktokenTests.cs
+++ b/test/Microsoft.ML.Tokenizers.Tests/TiktokenTests.cs
@@ -37,6 +37,7 @@ public class TiktokenTests
         public static Tokenizer GPT4o { get; } = TiktokenTokenizer.CreateForModel("gpt-4o");
         public static Tokenizer GPT5 { get; } = TiktokenTokenizer.CreateForModel("gpt-5");
         public static Tokenizer GPT5_1 { get; } = TiktokenTokenizer.CreateForModel("gpt-5.1");
+        public static Tokenizer GPT5_2 { get; } = TiktokenTokenizer.CreateForModel("gpt-5.2");
         public static Tokenizer Phi4 { get; } = TiktokenTokenizer.CreateForModel("phi-4");
         public static TiktokenTokenizer GptOss { get; } = TiktokenTokenizer.CreateForModel("gpt-oss-20b");
 
@@ -287,7 +288,7 @@ public void TestEncode5()
         [Fact]
         public void TestEncodeO200kBaseEncoding()
         {
-            foreach (TiktokenTokenizer tokenizer in new[] { GPT4o, GptOss, GPT5, GPT5_1 })
+            foreach (TiktokenTokenizer tokenizer in new[] { GPT4o, GptOss, GPT5, GPT5_1, GPT5_2 })
             {
                 string text = ReadAndSanitizeFile("./Data/lib.rs.txt");
                 IReadOnlyList<int> encoded = tokenizer.EncodeToIds(text);
@@ -418,6 +419,8 @@ public void TestEncodeR50kBase()
         [InlineData("gpt-5-chat")]
         [InlineData("gpt-5.1")]
         [InlineData("gpt-5.1-mini")]
+        [InlineData("gpt-5.2")]
+        [InlineData("gpt-5.2-mini")]
         [InlineData("chatgpt-4o-")]
         [InlineData("gpt-4")]
         [InlineData("gpt-4-")]
@@ -537,6 +540,7 @@ public void TestEncodingNamesNegativeCases()
         [InlineData("gpt-4o")]
         [InlineData("gpt-5")]
         [InlineData("gpt-5.1")]
+        [InlineData("gpt-5.2")]
         [InlineData("o1")]
         [InlineData("o3")]
         [InlineData("o4-mini")]