diff --git a/importlib_metadata/_adapters.py b/importlib_metadata/_adapters.py
index 3c5a7db9..e67941ee 100644
--- a/importlib_metadata/_adapters.py
+++ b/importlib_metadata/_adapters.py
@@ -132,7 +132,13 @@ def json(self):
         def transform(key):
             value = self.get_all(key) if key in self.multiple_use_keys else self[key]
             if key == 'Keywords':
-                value = re.split(r'\s+', value)
+                # Core Metadata separates keywords with commas; older
+                # metadata (and PEP 566) used whitespace.
+                value = (
+                    [keyword.strip() for keyword in value.split(',')]
+                    if ',' in value
+                    else re.split(r'\s+', value)
+                )
             tk = key.lower().replace('-', '_')
             return tk, value
 
diff --git a/newsfragments/+json-keywords.bugfix.rst b/newsfragments/+json-keywords.bugfix.rst
new file mode 100644
index 00000000..c37d0f2a
--- /dev/null
+++ b/newsfragments/+json-keywords.bugfix.rst
@@ -0,0 +1 @@
+Split comma-separated ``Keywords`` into separate items in JSON-compatible metadata, since Core Metadata separates keywords with commas.
diff --git a/tests/test_api.py b/tests/test_api.py
index 2d660b3d..76b06e15 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -311,6 +311,24 @@ def test_as_json_odd_case(self):
         assert len(md['requires_dist']) == 2
         assert md['keywords'] == ['SAMPLE', 'PACKAGE']
 
+    @fixtures.parameterize(
+        dict(value='sample,package', expected=['sample', 'package']),
+        dict(value='sample, package', expected=['sample', 'package']),
+        dict(value='sample package,tool', expected=['sample package', 'tool']),
+    )
+    def test_as_json_comma_separated_keywords(self, value, expected):
+        """
+        Core Metadata and the tools that write it separate keywords with
+        commas.
+        """
+        content = (
+            'Metadata-Version: 2.4\nName: distinfo-pkg\nVersion: 1.0.0\n'
+            f'Keywords: {value}\n'
+        )
+        path = self.site_dir / 'distinfo_pkg-1.0.0.dist-info' / 'METADATA'
+        path.write_text(content, encoding='utf-8')
+        assert metadata('distinfo-pkg').json['keywords'] == expected
+
 
 class LegacyDots(fixtures.DistInfoPkgWithDotLegacy, unittest.TestCase):
     def test_name_normalization(self):