diff --git a/src/cloudflare/resources/kv/namespaces/values.py b/src/cloudflare/resources/kv/namespaces/values.py
index 05e3e187510..c65aa933923 100644
--- a/src/cloudflare/resources/kv/namespaces/values.py
+++ b/src/cloudflare/resources/kv/namespaces/values.py
@@ -113,6 +113,10 @@ def update(
             raise ValueError(f"Expected a non-empty value for `namespace_id` but received {namespace_id!r}")
         if not key_name:
             raise ValueError(f"Expected a non-empty value for `key_name` but received {key_name!r}")
+        # It should be noted that the actual Content-Type header that will be
+        # sent to the server will contain a `boundary` parameter, e.g.
+        # multipart/form-data; boundary=---abc--
+        extra_headers = {"Content-Type": "multipart/form-data", **(extra_headers or {})}
         return self._put(
             f"/accounts/{account_id}/storage/kv/namespaces/{namespace_id}/values/{key_name}",
             body=maybe_transform(
@@ -324,6 +328,10 @@ async def update(
             raise ValueError(f"Expected a non-empty value for `namespace_id` but received {namespace_id!r}")
         if not key_name:
             raise ValueError(f"Expected a non-empty value for `key_name` but received {key_name!r}")
+        # It should be noted that the actual Content-Type header that will be
+        # sent to the server will contain a `boundary` parameter, e.g.
+        # multipart/form-data; boundary=---abc--
+        extra_headers = {"Content-Type": "multipart/form-data", **(extra_headers or {})}
         return await self._put(
             f"/accounts/{account_id}/storage/kv/namespaces/{namespace_id}/values/{key_name}",
             body=await async_maybe_transform(
diff --git a/tests/api_resources/kv/namespaces/test_values.py b/tests/api_resources/kv/namespaces/test_values.py
index fbf0e7a0dd5..40de31a73df 100644
--- a/tests/api_resources/kv/namespaces/test_values.py
+++ b/tests/api_resources/kv/namespaces/test_values.py
@@ -115,6 +115,40 @@ def test_path_params_update(self, client: Cloudflare) -> None:
                 value="Some Value",
             )
 
+    @parametrize
+    @pytest.mark.respx(base_url=base_url)
+    def test_update_uses_multipart_form_data(self, client: Cloudflare, respx_mock: MockRouter) -> None:
+        """Test that values.update sends data as multipart/form-data, not JSON.
+
+        This is a regression test for https://github.com/cloudflare/cloudflare-python/issues/2519
+        """
+        respx_mock.put(
+            "/accounts/023e105f4ecef8ad9ca31a8372d0c353/storage/kv/namespaces/0f2ac74b498b48028cb68387c421e279/values/My-Key"
+        ).mock(return_value=httpx.Response(200, json={"success": True, "result": {}}))
+
+        client.kv.namespaces.values.update(
+            key_name="My-Key",
+            account_id="023e105f4ecef8ad9ca31a8372d0c353",
+            namespace_id="0f2ac74b498b48028cb68387c421e279",
+            metadata='{"someMetadataKey": "someMetadataValue"}',
+            value="Some Value",
+        )
+
+        # Verify the request was made
+        assert respx_mock.calls.call_count == 1
+        request = respx_mock.calls[0].request
+
+        # Verify Content-Type is multipart/form-data (with boundary)
+        content_type = request.headers.get("content-type", "")
+        assert content_type.startswith("multipart/form-data"), (
+            f"Expected Content-Type to start with 'multipart/form-data', got '{content_type}'"
+        )
+
+        # Verify the body contains separate form fields for value and metadata
+        body = request.content.decode("utf-8")
+        assert "Some Value" in body, "Value should be in the multipart body"
+        assert "someMetadataKey" in body, "Metadata should be in the multipart body"
+
     @parametrize
     def test_method_delete(self, client: Cloudflare) -> None:
         value = client.kv.namespaces.values.delete(
@@ -351,6 +385,40 @@ async def test_path_params_update(self, async_client: AsyncCloudflare) -> None:
                 value="Some Value",
             )
 
+    @parametrize
+    @pytest.mark.respx(base_url=base_url)
+    async def test_update_uses_multipart_form_data(self, async_client: AsyncCloudflare, respx_mock: MockRouter) -> None:
+        """Test that values.update sends data as multipart/form-data, not JSON.
+
+        This is a regression test for https://github.com/cloudflare/cloudflare-python/issues/2519
+        """
+        respx_mock.put(
+            "/accounts/023e105f4ecef8ad9ca31a8372d0c353/storage/kv/namespaces/0f2ac74b498b48028cb68387c421e279/values/My-Key"
+        ).mock(return_value=httpx.Response(200, json={"success": True, "result": {}}))
+
+        await async_client.kv.namespaces.values.update(
+            key_name="My-Key",
+            account_id="023e105f4ecef8ad9ca31a8372d0c353",
+            namespace_id="0f2ac74b498b48028cb68387c421e279",
+            metadata='{"someMetadataKey": "someMetadataValue"}',
+            value="Some Value",
+        )
+
+        # Verify the request was made
+        assert respx_mock.calls.call_count == 1
+        request = respx_mock.calls[0].request
+
+        # Verify Content-Type is multipart/form-data (with boundary)
+        content_type = request.headers.get("content-type", "")
+        assert content_type.startswith("multipart/form-data"), (
+            f"Expected Content-Type to start with 'multipart/form-data', got '{content_type}'"
+        )
+
+        # Verify the body contains separate form fields for value and metadata
+        body = request.content.decode("utf-8")
+        assert "Some Value" in body, "Value should be in the multipart body"
+        assert "someMetadataKey" in body, "Metadata should be in the multipart body"
+
     @parametrize
     async def test_method_delete(self, async_client: AsyncCloudflare) -> None:
         value = await async_client.kv.namespaces.values.delete(