diff --git a/CHANGES.rst b/CHANGES.rst
index 72754ad6..7b6a96cd 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -6,7 +6,7 @@ Version 2.1.0
 Unreleased
 
 -   Update Click dependency to >= 8.0.
-
+-   Added support for Decimal objects in JSONEncoder
 
 Version 2.0.2
 -------------
diff --git a/src/flask/json/__init__.py b/src/flask/json/__init__.py
index 5780e204..edcbd95d 100644
--- a/src/flask/json/__init__.py
+++ b/src/flask/json/__init__.py
@@ -1,3 +1,4 @@
+import decimal
 import io
 import json as _json
 import typing as t
@@ -45,6 +46,8 @@ class JSONEncoder(_json.JSONEncoder):
         overriding how basic types like ``str`` or ``list`` are
         serialized, they are handled before this method.
         """
+        if isinstance(o, decimal.Decimal):
+            return str(o)
         if isinstance(o, date):
             return http_date(o)
         if isinstance(o, uuid.UUID):
diff --git a/tests/test_json.py b/tests/test_json.py
index fb8bdcba..fd758dc2 100644
--- a/tests/test_json.py
+++ b/tests/test_json.py
@@ -1,4 +1,5 @@
 import datetime
+import decimal
 import io
 import uuid
 
@@ -9,6 +10,11 @@ import flask
 from flask import json
 
 
+def test_json_encode_decimal():
+    decimal_ = decimal.Decimal(100)
+    assert flask.json.JSONEncoder().default(decimal_) == str(decimal_)
+
+
 @pytest.mark.parametrize("debug", (True, False))
 def test_bad_request_debug_message(app, client, debug):
     app.config["DEBUG"] = debug