diff --git a/changelog/4462.changed.md b/changelog/4462.changed.md
new file mode 100644
index 000000000..c5e5947aa
--- /dev/null
+++ b/changelog/4462.changed.md
@@ -0,0 +1 @@
+- Updated the default model for `CartesiaTTSService` and `CartesiaHttpTTSService` from `sonic-3` to `sonic-3.5`.
diff --git a/src/pipecat/services/cartesia/tts.py b/src/pipecat/services/cartesia/tts.py
index d88f462c5..5a2aa04f7 100644
--- a/src/pipecat/services/cartesia/tts.py
+++ b/src/pipecat/services/cartesia/tts.py
@@ -304,7 +304,7 @@ class CartesiaTTSService(WebsocketTTSService):
 
         # 1. Initialize default_settings with hardcoded defaults
         default_settings = self.Settings(
-            model="sonic-3",
+            model="sonic-3.5",
             voice=None,
             language=Language.EN,
             generation_config=None,
@@ -801,7 +801,7 @@ class CartesiaHttpTTSService(TTSService):
         """
         # 1. Initialize default_settings with hardcoded defaults
         default_settings = self.Settings(
-            model="sonic-3",
+            model="sonic-3.5",
             voice=None,
             language=Language.EN,
             generation_config=None,