diff --git a/.gitignore b/.gitignore
index cb3efa641..7f90bd510 100644
--- a/.gitignore
+++ b/.gitignore
@@ -93,3 +93,6 @@ testing_support/google_appengine
 
 # Ignore VsChromium configuration file.
 /vs-chromium-project.txt
+
+# Ignore the file that logs Python 2 scripts run during presubmits.
+/python2_usage.txt
diff --git a/presubmit_support.py b/presubmit_support.py
index 30c003601..679c0c145 100755
--- a/presubmit_support.py
+++ b/presubmit_support.py
@@ -1725,6 +1725,10 @@ def DoPresubmitChecks(change,
     if not presubmit_files and verbose:
       sys.stdout.write('Warning, no PRESUBMIT.py found.\n')
     results = []
+    depot_tools = os.path.dirname(os.path.abspath(__file__))
+    python2_usage_log_file = os.path.join(depot_tools, 'python2_usage.txt')
+    if os.path.exists(python2_usage_log_file):
+      os.remove(python2_usage_log_file)
     thread_pool = ThreadPool()
     executer = PresubmitExecuter(change, committing, verbose, gerrit_obj,
                                  dry_run, thread_pool, parallel, use_python3,
@@ -1751,6 +1755,17 @@ def DoPresubmitChecks(change,
 
     results += thread_pool.RunAsync()
 
+    if os.path.exists(python2_usage_log_file):
+      with open(python2_usage_log_file) as f:
+        python2_usage = [x.strip() for x in f.readlines()]
+        results.append(
+            OutputApi(committing).PresubmitPromptWarning(
+                'Python 2 scripts were run during %s presubmits. Please see '
+                'https://bugs.chromium.org/p/chromium/issues/detail?id=1313804'
+                '#c61 for tips on resolving this.'
+                % python_version,
+                items=python2_usage))
+
     messages = {}
     should_prompt = False
     presubmits_failed = False
diff --git a/vpython b/vpython
index 997658acc..c63795471 100755
--- a/vpython
+++ b/vpython
@@ -41,6 +41,8 @@ base_dir=$(dirname "$0")
 source "$base_dir/cipd_bin_setup.sh"
 cipd_bin_setup &> /dev/null
 
+echo $@ from $(pwd) >> "$base_dir/python2_usage.txt"
+
 # If Python bootstrapping is not disabled, make sure Python has been
 # bootstrapped and add it to the front of PATH.
 if [[ $(uname -s) = MINGW* || $(uname -s) = CYGWIN* ]]; then
diff --git a/vpython.bat b/vpython.bat
index 0b1826172..43f00cf79 100644
--- a/vpython.bat
+++ b/vpython.bat
@@ -6,4 +6,5 @@
 :: See revert instructions in cipd_manifest.txt
 
 call "%~dp0\cipd_bin_setup.bat" > nul 2>&1
+echo %* from %cd% >> "%~dp0\python2_usage.txt"
 "%~dp0\.cipd_bin\vpython.exe" -vpython-interpreter "%~dp0\python.bat" %*