diff --git a/tests/test_api_client/test_serializer.py b/tests/test_api_client/test_serializer.py
index b190bf15..a8bd549c 100644
--- a/tests/test_api_client/test_serializer.py
+++ b/tests/test_api_client/test_serializer.py
@@ -3,6 +3,7 @@
 from datetime import date, datetime, timedelta
 from decimal import Decimal
 from unittest import mock
+from uuid import UUID
 
 import pytest
 from dateutil import tz
@@ -389,3 +390,14 @@ def test_serialize_enum_model(value, expected):
     # then correct enum value expected
     assert isinstance(result, str)
     assert result == expected
+
+
+# serialize UUID tests (regression for #161)
+def test_serialize_uuid():
+    # given a UUID value (e.g. an invoice id returned by the Xero API)
+    value = UUID("12345678-1234-5678-1234-567812345678")
+    # when serializing it
+    result = serialize(value)
+    # then it becomes the canonical hyphenated string, not a ValueError
+    assert isinstance(result, str)
+    assert result == "12345678-1234-5678-1234-567812345678"
diff --git a/xero_python/api_client/serializer.py b/xero_python/api_client/serializer.py
index cf508da9..f2cc2b3f 100644
--- a/xero_python/api_client/serializer.py
+++ b/xero_python/api_client/serializer.py
@@ -3,6 +3,7 @@
 from datetime import datetime, time, date
 from enum import Enum
 from functools import singledispatch
+from uuid import UUID
 
 from dateutil import tz
 
@@ -221,3 +222,15 @@ def serialize_enum_model(model):
     :return: serialized object
     """
     return model.value
+
+
+@serialize_model.register(UUID)
+def serialize_uuid_model(model):
+    """Serializes a UUID into a json serializable string.
+
+    Uses the canonical 8-4-4-4-12 hyphenated form expected by the Xero API.
+
+    :param model: UUID instance to serialize
+    :return: serialized object
+    """
+    return str(model)