diff --git a/sdk/eventhub/azure-eventhub/tests/pyamqp_tests/unittest/test_link.py b/sdk/eventhub/azure-eventhub/tests/pyamqp_tests/unittest/test_link.py
index 6fef311f1d58..ba66d083e57b 100644
--- a/sdk/eventhub/azure-eventhub/tests/pyamqp_tests/unittest/test_link.py
+++ b/sdk/eventhub/azure-eventhub/tests/pyamqp_tests/unittest/test_link.py
@@ -3,6 +3,9 @@
 from azure.eventhub._pyamqp.link import Link
 from azure.eventhub._pyamqp.receiver import ReceiverLink
 from azure.eventhub._pyamqp.constants import LinkState
+from azure.eventhub._pyamqp.link import Source, Target
+from unittest.mock import Mock, patch
+from azure.eventhub._pyamqp.constants import LINK_MAX_MESSAGE_SIZE
 import pytest
 
 
@@ -84,6 +87,73 @@ def test_receive_transfer_frame_multiple():
     link._incoming_transfer(transfer_frame_two)
     assert link.current_link_credit == 1
 
+def test_max_message_size_negotiation_with_client_unlimited():
+    """
+    Test AMQP attach frame negotiation where client sends max_message_size=0 (unlimited)
+    and server responds with its limit (20MB), resulting in final size of 20MB.
+    
+    """
+    mock_session = Mock()
+    mock_connection = Mock()
+    mock_session._connection = mock_connection
+
+    SERVER_MAX_MESSAGE_SIZE = 20 * 1024 * 1024 
+
+    link = Link(
+        mock_session,
+        3,
+        name="test_link",
+        role=False,  # Sender role
+        source_address="test_source", 
+        target_address="test_target",
+        network_trace=False,
+        network_trace_params={},
+        max_message_size=LINK_MAX_MESSAGE_SIZE
+    )
+
+    # Verifying that client sends 0 (unlimited) in attach frame
+    assert link.max_message_size == 0, f"Expected client max_message_size=0, got {link._max_message_size}"
+    # Simulating server's attach response with 20MB limit, Mock incoming attach frame from server
+    mock_attach_frame = [
+    "test_link",          
+    3,                    
+    False,               
+    0,                    
+    1,                    
+    Source(address="test_source"),  
+    Target(address="test_target"), 
+    None,                 
+    False,              
+    None,                 
+    20 * 1024 * 1024,     
+    None,                 
+    None,                 
+    None,      ]
+
+    # Testing _outgoing_attach()
+    with patch.object(link, '_outgoing_attach') as mock_outgoing_attach:
+        # Trigger outgoing attach
+        link.attach()
+
+        # Verifying _outgoing_attach was called
+        assert mock_outgoing_attach.called, "_outgoing_attach should have been called during attach()"
+
+        # Get the attach frame that would be sent to server
+        call_args = mock_outgoing_attach.call_args
+        if call_args and call_args[0]:
+            attach_frame = call_args[0][0]
+            assert attach_frame.max_message_size == 0, f"Expected client to send max_message_size=0, got {attach_frame.max_message_size}"
+
+    # Testing _incoming_attach()
+    with patch.object(link, '_outgoing_attach') as mock_outgoing_response:
+
+        # Calling _incoming_attach to process server's response
+        link._incoming_attach(mock_attach_frame)
+
+        expected_final_size = SERVER_MAX_MESSAGE_SIZE
+        # Verifying remote_max_message_size is set correctly
+        assert link.remote_max_message_size == expected_final_size, \
+        f"Expected remote_max_message_size={SERVER_MAX_MESSAGE_SIZE}, got {link.remote_max_message_size}"
 
 def test_receive_transfer_continuation_frame():
     session = None