diff --git a/python/semantic_kernel/prompt_template/prompt_template_config.py b/python/semantic_kernel/prompt_template/prompt_template_config.py
index 7124f73e5e38..da836c173cca 100644
--- a/python/semantic_kernel/prompt_template/prompt_template_config.py
+++ b/python/semantic_kernel/prompt_template/prompt_template_config.py
@@ -71,10 +71,14 @@ def rewrite_execution_settings(
 
     def add_execution_settings(self, settings: PromptExecutionSettings, overwrite: bool = True) -> None:
         """Add execution settings to the prompt template."""
-        if settings.service_id in self.execution_settings and not overwrite:
+        # Check existence with the same key that storage uses: when service_id is None the settings are
+        # stored under DEFAULT_SERVICE_NAME, so testing service_id (None) never matches and overwrite=False
+        # silently has no effect (see issue #14582).
+        key = settings.service_id or DEFAULT_SERVICE_NAME
+        if key in self.execution_settings and not overwrite:
+            logger.warning("Execution settings already exist and overwrite is set to False")
             return
-        self.execution_settings[settings.service_id or DEFAULT_SERVICE_NAME] = settings
-        logger.warning("Execution settings already exist and overwrite is set to False")
+        self.execution_settings[key] = settings
 
     def get_kernel_parameter_metadata(self) -> Sequence[KernelParameterMetadata]:
         """Get the kernel parameter metadata for the input variables."""
diff --git a/python/tests/unit/prompt_template/test_prompt_templates.py b/python/tests/unit/prompt_template/test_prompt_templates.py
index 80e345f2431c..61916c5c8033 100644
--- a/python/tests/unit/prompt_template/test_prompt_templates.py
+++ b/python/tests/unit/prompt_template/test_prompt_templates.py
@@ -2,6 +2,7 @@
 
 
 import json
+import logging
 
 import yaml
 from pytest import raises
@@ -72,6 +73,32 @@ def test_add_execution_settings_with_overwrite():
     assert config.execution_settings["test"].extension_data["setting_value"] == "new_value2"
 
 
+def test_add_execution_settings_no_overwrite_default_service():
+    """overwrite=False protects the entry stored under DEFAULT_SERVICE_NAME (service_id is None)."""
+    config = PromptTemplateConfig(template="Example template")
+    first = PromptExecutionSettings(extension_data={"temperature": 0.1})
+    config.add_execution_settings(first)
+    assert config.execution_settings["default"] == first
+
+    second = PromptExecutionSettings(extension_data={"temperature": 0.9})
+    config.add_execution_settings(second, overwrite=False)
+    assert config.execution_settings["default"].extension_data["temperature"] == 0.1
+
+
+def test_add_execution_settings_warning_only_when_refused(caplog):
+    """The "already exists" warning is emitted only when an add is refused, not after every add."""
+    with caplog.at_level(logging.WARNING):
+        config = PromptTemplateConfig(template="Example template")
+        settings = PromptExecutionSettings(extension_data={"temperature": 0.1})
+        config.add_execution_settings(settings, overwrite=False)
+        assert "overwrite is set to False" not in caplog.text
+
+        caplog.clear()
+        other = PromptExecutionSettings(extension_data={"temperature": 0.9})
+        config.add_execution_settings(other, overwrite=False)
+        assert "overwrite is set to False" in caplog.text
+
+
 def test_get_kernel_parameter_metadata_empty():
     config = PromptTemplateConfig(template="Example template")
     metadata = config.get_kernel_parameter_metadata()