diff --git a/Lib/json/tool.py b/Lib/json/tool.py
--- a/Lib/json/tool.py
+++ b/Lib/json/tool.py
@@ -12,16 +12,25 @@ Usage::
 """
 import sys
 import json
 
 def main():
     if len(sys.argv) == 1:
         infile = sys.stdin
         outfile = sys.stdout
+    elif len(sys.argv) == 2 and sys.argv[1] in {'-h', '--help'}:
+        usage = """usage: %s -m json.tool [infile [outfile]]
+
+optional arguments:
+
+  -h, --help            show this help message and exit
+        """
+        print(usage % sys.executable)
+        sys.exit(0)
     elif len(sys.argv) == 2:
         infile = open(sys.argv[1], 'r')
         outfile = sys.stdout
     elif len(sys.argv) == 3:
         infile = open(sys.argv[1], 'r')
         outfile = open(sys.argv[2], 'w')
     else:
         raise SystemExit(sys.argv[0] + " [infile [outfile]]")
diff --git a/Lib/test/test_json/test_tool.py b/Lib/test/test_json/test_tool.py
--- a/Lib/test/test_json/test_tool.py
+++ b/Lib/test/test_json/test_tool.py
@@ -62,8 +62,14 @@ class TestTool(unittest.TestCase):
         infile = self._create_infile()
         outfile = support.TESTFN + '.out'
         rc, out, err = assert_python_ok('-m', 'json.tool', infile, outfile)
         self.addCleanup(os.remove, outfile)
         with open(outfile, "r") as fp:
             self.assertEqual(fp.read(), self.expect)
         self.assertEqual(out, b'')
         self.assertEqual(err, b'')
+
+    def test_help_flag(self):
+        rc, out, err = assert_python_ok('-m', 'json.tool', '-h')
+        self.assertEqual(rc, 0)
+        self.assertTrue(out.startswith(b'usage: '))
+        self.assertEqual(err, b'')