diff --git a/tests/test_models.py b/tests/test_models.py
new file mode 100644
index 00000000..5dbfb1b3
--- /dev/null
+++ b/tests/test_models.py
@@ -0,0 +1,59 @@
+# -*- coding: utf-8 -*-
+"""
+Tests for xero_python.models.BaseModel.to_dict serialization.
+
+Regression test for #93: BaseModel.to_dict() must return JSON-serializable
+primitives. Previously enum-typed (and UUID-typed) attributes were returned
+as the raw Enum / UUID object, so json.dumps(model.to_dict()) raised.
+"""
+import json
+from enum import Enum
+from uuid import UUID
+
+from xero_python.models import BaseModel
+
+
+class AccountType(Enum):
+    BANK = "BANK"
+    EXPENSE = "EXPENSE"
+
+
+class Journal(BaseModel):
+    openapi_types = {"account_type": "AccountType", "journal_id": "UUID", "name": "str"}
+    attribute_map = {
+        "account_type": "AccountType",
+        "journal_id": "JournalID",
+        "name": "Name",
+    }
+
+    def __init__(self, **kwargs):
+        # mirror generated models: every declared attribute defaults to None
+        for name in self.openapi_types:
+            setattr(self, name, None)
+        for name, value in kwargs.items():
+            setattr(self, name, value)
+
+
+def test_to_dict_serializes_enum_to_its_value():
+    journal = Journal(account_type=AccountType.BANK)
+    assert journal.to_dict()["account_type"] == "BANK"
+
+
+def test_to_dict_serializes_uuid_to_string():
+    journal = Journal(journal_id=UUID("12345678-1234-5678-1234-567812345678"))
+    assert journal.to_dict()["journal_id"] == "12345678-1234-5678-1234-567812345678"
+
+
+def test_to_dict_is_json_serializable():
+    journal = Journal(
+        account_type=AccountType.EXPENSE,
+        journal_id=UUID("12345678-1234-5678-1234-567812345678"),
+        name="Sales",
+    )
+    # should not raise
+    encoded = json.dumps(journal.to_dict())
+    assert json.loads(encoded) == {
+        "account_type": "EXPENSE",
+        "journal_id": "12345678-1234-5678-1234-567812345678",
+        "name": "Sales",
+    }
diff --git a/xero_python/models.py b/xero_python/models.py
index e13fbdfa..09433a26 100644
--- a/xero_python/models.py
+++ b/xero_python/models.py
@@ -1,6 +1,8 @@
 # -*- coding: utf-8 -*-
 import pprint
+from enum import Enum
 from functools import singledispatch
+from uuid import UUID
 
 
 class BaseModel:
@@ -67,3 +69,13 @@ def serialize_tuple_to_dict(value):
 @serialize_to_dict.register(dict)
 def serialize_dict_to_dict(value):
     return {key: serialize_to_dict(val) for key, val in value.items()}
+
+
+@serialize_to_dict.register(Enum)
+def serialize_enum_to_dict(value):
+    return value.value
+
+
+@serialize_to_dict.register(UUID)
+def serialize_uuid_to_dict(value):
+    return str(value)