diff --git a/llvm/utils/lit/lit/formats/googletest.py b/llvm/utils/lit/lit/formats/googletest.py
--- a/llvm/utils/lit/lit/formats/googletest.py
+++ b/llvm/utils/lit/lit/formats/googletest.py
@@ -112,8 +112,8 @@
         shard_env = {
             'GTEST_OUTPUT': 'json:' + test.gtest_json_file,
             'GTEST_SHUFFLE': '1' if use_shuffle else '0',
-            'GTEST_TOTAL_SHARDS': total_shards,
-            'GTEST_SHARD_INDEX': shard_idx
+            'GTEST_TOTAL_SHARDS': os.environ.get("GTEST_TOTAL_SHARDS", total_shards),
+            'GTEST_SHARD_INDEX': os.environ.get("GTEST_SHARD_INDEX", shard_idx)
         }
         test.config.environment.update(shard_env)
 
diff --git a/llvm/utils/lit/tests/Inputs/googletest-format-respect-gtest-sharding-env-vars/DummySubDir/OneTest.py b/llvm/utils/lit/tests/Inputs/googletest-format-respect-gtest-sharding-env-vars/DummySubDir/OneTest.py
new file mode 100644
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/googletest-format-respect-gtest-sharding-env-vars/DummySubDir/OneTest.py
@@ -0,0 +1,108 @@
+#!/usr/bin/env python
+
+import os
+import sys
+
+if len(sys.argv) == 3 and sys.argv[1] == "--gtest_list_tests":
+    if sys.argv[2] != '--gtest_filter=-*DISABLED_*':
+        raise ValueError("unexpected argument: %s" % (sys.argv[2]))
+    print("""\
+FirstTest.
+  subTestA
+  subTestB
+  subTestC
+  subTestD
+ParameterizedTest/0.
+  subTest
+ParameterizedTest/1.
+  subTest""")
+    sys.exit(0)
+elif len(sys.argv) != 1:
+    # sharding and json output are specified using environment variables
+    raise ValueError("unexpected argument: %r" % (' '.join(sys.argv[1:])))
+
+for e in ['GTEST_TOTAL_SHARDS', 'GTEST_SHARD_INDEX', 'GTEST_OUTPUT']:
+    if e not in os.environ:
+        raise ValueError("missing environment variables: " + e)
+
+if not os.environ['GTEST_OUTPUT'].startswith('json:'):
+    raise ValueError("must emit json output: " + os.environ['GTEST_OUTPUT'])
+
+output = """\
+{
+"random_seed": 123,
+"testsuites": [
+    {
+        "name": "FirstTest",
+        "testsuite": [
+            {
+                "name": "subTestA",
+                "result": "COMPLETED",
+                "time": "0.001s"
+            },
+            {
+                "name": "subTestB",
+                "result": "COMPLETED",
+                "time": "0.001s",
+                "failures": [
+                    {
+                        "failure": "I am subTest B, I FAIL\\nAnd I have two lines of output",
+                        "type": ""
+                    }
+                ]
+            },
+            {
+                "name": "subTestC",
+                "result": "SKIPPED",
+                "time": "0.001s"
+            },
+            {
+                "name": "subTestD",
+                "result": "UNRESOLVED",
+                "time": "0.001s"
+            }
+        ]
+    },
+    {
+        "name": "ParameterizedTest/0",
+        "testsuite": [
+            {
+                "name": "subTest",
+                "result": "COMPLETED",
+                "time": "0.001s"
+            }
+        ]
+    },
+    {
+        "name": "ParameterizedTest/1",
+        "testsuite": [
+            {
+                "name": "subTest",
+                "result": "COMPLETED",
+                "time": "0.001s"
+            }
+        ]
+    }
+]
+}"""
+
+dummy_output = """\
+{
+"testsuites": [
+]
+}"""
+
+json_filename = os.environ['GTEST_OUTPUT'].split(':', 1)[1]
+with open(json_filename, 'w', encoding='utf-8') as f:
+    if os.environ['GTEST_TOTAL_SHARDS'] == '1':
+        print('[ RUN      ] FirstTest.subTestB', flush=True)
+        print('I am subTest B output', file=sys.stderr, flush=True)
+        print('[  FAILED  ] FirstTest.subTestB (8 ms)', flush=True)
+
+        f.write(output)
+        exit_code = 1
+    else:
+        f.write(dummy_output)
+        exit_code = 0
+
+sys.exit(exit_code)
diff --git a/llvm/utils/lit/tests/Inputs/googletest-format-respect-gtest-sharding-env-vars/lit.cfg b/llvm/utils/lit/tests/Inputs/googletest-format-respect-gtest-sharding-env-vars/lit.cfg
new file mode 100644
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/googletest-format-respect-gtest-sharding-env-vars/lit.cfg
@@ -0,0 +1,3 @@
+import lit.formats
+config.name = 'googletest-format'
+config.test_format = lit.formats.GoogleTest('DummySubDir', 'Test')
diff --git a/llvm/utils/lit/tests/googletest-format-respect-gtest-sharding-env-vars.py b/llvm/utils/lit/tests/googletest-format-respect-gtest-sharding-env-vars.py
new file mode 100644
--- /dev/null
+++ b/llvm/utils/lit/tests/googletest-format-respect-gtest-sharding-env-vars.py
@@ -0,0 +1,18 @@
+# Check GTEST_TOTAL_SHARDS and GTEST_SHARD_INDEX environment variabls are
+# respected when using the googletest formatter.
+
+# RUN: env GTEST_TOTAL_SHARDS=1 GTEST_SHARD_INDEX=0 \
+# RUN: not %{lit} -v --order=random %{inputs}/googletest-format-respect-gtest-sharding-env-vars > %t.out
+# FIXME: Temporarily dump test output so we can debug failing tests on
+# buildbots.
+# RUN: cat %t.out
+# RUN: FileCheck < %t.out %s
+#
+# END.
+
+# CHECK: -- Testing:
+# CHECK: FAIL: googletest-format :: [[PATH:[Dd]ummy[Ss]ub[Dd]ir/]][[FILE:OneTest\.py]]/0
+# CHECK: *** TEST 'googletest-format :: [[PATH]][[FILE]]/0{{.*}} FAILED ***
+# CHECK-NEXT: Script(shard):
+# CHECK-NEXT: --
+# CHECK-NEXT: GTEST_OUTPUT=json:{{[^[:space:]]*}} GTEST_SHUFFLE=1 GTEST_TOTAL_SHARDS=1 GTEST_SHARD_INDEX=0 GTEST_RANDOM_SEED=123 {{.*}}[[FILE]]