diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6a1e33938a..adb07aa288 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- `opentelemetry-api`: Fix AttributeError on invalid attribute type in Python 3.9
+  ([#4905](https://github.com/open-telemetry/opentelemetry-python/pull/4905))
 - `opentelemetry-exporter-otlp-proto-grpc`: Fix re-initialization of gRPC channel on UNAVAILABLE error
   ([#4825](https://github.com/open-telemetry/opentelemetry-python/pull/4825))
 - `opentelemetry-exporter-prometheus`: Fix duplicate HELP/TYPE declarations for metrics with different label sets
diff --git a/opentelemetry-api/src/opentelemetry/attributes/__init__.py b/opentelemetry-api/src/opentelemetry/attributes/__init__.py
index 5116c2fdd8..a2995b9086 100644
--- a/opentelemetry-api/src/opentelemetry/attributes/__init__.py
+++ b/opentelemetry-api/src/opentelemetry/attributes/__init__.py
@@ -39,6 +39,11 @@
 _logger = logging.getLogger(__name__)
 
 
+def _get_type_name(type_: type) -> str:
+    """Get the name of a type, handling typing generics that may lack __name__."""
+    return getattr(type_, "__name__", str(type_))
+
+
 def _clean_attribute(
     key: str, value: types.AttributeValue, max_len: Optional[int]
 ) -> Optional[Union[types.AttributeValue, Tuple[Union[str, int, float], ...]]]:
@@ -83,7 +88,7 @@ def _clean_attribute(
                     element_type.__name__,
                     key,
                     [
-                        valid_type.__name__
+                        _get_type_name(valid_type)
                         for valid_type in _VALID_ATTR_VALUE_TYPES
                     ],
                 )
@@ -113,7 +118,7 @@ def _clean_attribute(
         "sequence of those types",
         type(value).__name__,
         key,
-        [valid_type.__name__ for valid_type in _VALID_ATTR_VALUE_TYPES],
+        [_get_type_name(valid_type) for valid_type in _VALID_ATTR_VALUE_TYPES],
     )
     return None
 
@@ -190,7 +195,7 @@ def _clean_extended_attribute_value(  # pylint: disable=too-many-branches
     except Exception:
         raise TypeError(
             f"Invalid type {type(value).__name__} for attribute value. "
-            f"Expected one of {[valid_type.__name__ for valid_type in _VALID_ANY_VALUE_TYPES]} or a "
+            f"Expected one of {[_get_type_name(valid_type) for valid_type in _VALID_ANY_VALUE_TYPES]} or a "
             "sequence of those types",
         )
 
diff --git a/opentelemetry-api/tests/attributes/test_attributes.py b/opentelemetry-api/tests/attributes/test_attributes.py
index 8cb6f35fbc..2a235ed937 100644
--- a/opentelemetry-api/tests/attributes/test_attributes.py
+++ b/opentelemetry-api/tests/attributes/test_attributes.py
@@ -16,11 +16,13 @@
 
 import unittest
 from typing import MutableSequence
+from unittest import mock
 
 from opentelemetry.attributes import (
     BoundedAttributes,
     _clean_attribute,
     _clean_extended_attribute,
+    _clean_extended_attribute_value,
 )
 
 
@@ -182,6 +184,28 @@ def test_mapping(self):
             _clean_extended_attribute("headers", mapping, None), expected
         )
 
+    def test_invalid_type_error_message(self):
+        """Test that invalid types produce proper TypeError, not AttributeError.
+
+        Regression test for issue #4821 where typing.Mapping lacks __name__ in Python 3.9.
+        """
+
+        # Create a class that raises when converted to string
+        class InvalidType:
+            def __str__(self):
+                raise ValueError("Cannot convert to string")
+
+        # This should raise TypeError with expected types listed, not AttributeError
+        with self.assertRaises(TypeError) as ctx:
+            _clean_extended_attribute_value(InvalidType(), None)
+
+        # Verify the error message contains expected information and doesn't raise AttributeError
+        error_msg = str(ctx.exception)
+        self.assertIn("Invalid type", error_msg)
+        self.assertIn("InvalidType", error_msg)
+        # Ensure the message includes valid types without raising AttributeError
+        self.assertIn("Expected one of", error_msg)
+
 
 class TestBoundedAttributes(unittest.TestCase):
     # pylint: disable=consider-using-dict-items
@@ -294,7 +318,7 @@ def test_locking(self):
     # pylint: disable=no-self-use
     def test_extended_attributes(self):
         bdict = BoundedAttributes(extended_attributes=True, immutable=False)
-        with unittest.mock.patch(
+        with mock.patch(
             "opentelemetry.attributes._clean_extended_attribute",
             return_value="mock_value",
         ) as clean_extended_attribute_mock: