diff --git a/atst/utils/json.py b/atst/utils/json.py
new file mode 100644
index 00000000..a489fcaa
--- /dev/null
+++ b/atst/utils/json.py
@@ -0,0 +1,9 @@
+from flask.json import JSONEncoder
+from atst.models.attachment import Attachment
+
+
+class CustomJSONEncoder(JSONEncoder):
+    def default(self, obj):
+        if isinstance(obj, Attachment):
+            return obj.filename
+        return JSONEncoder.default(self, obj)
diff --git a/tests/utils/test_json.py b/tests/utils/test_json.py
new file mode 100644
index 00000000..5db25c17
--- /dev/null
+++ b/tests/utils/test_json.py
@@ -0,0 +1,15 @@
+import json
+from atst.utils.json import CustomJSONEncoder
+
+from tests.factories import AttachmentFactory
+
+
+encoder = CustomJSONEncoder()
+
+
+def test_custom_encoder_serializes_attachments():
+    filename = "jar_jar_is_secretly_a_sith_lord.pdf"
+    attachment = AttachmentFactory.create(filename=filename)
+    encoded = encoder.encode({"file": attachment})
+    expected = json.dumps({"file": filename})
+    assert encoded == expected