diff --git a/appengine/flexible/sendgrid/requirements-test.txt b/appengine/flexible/sendgrid/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/appengine/flexible/sendgrid/requirements-test.txt
+++ b/appengine/flexible/sendgrid/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/appengine/standard/endpoints-frameworks-v2/echo/requirements-test.txt b/appengine/standard/endpoints-frameworks-v2/echo/requirements-test.txt
index 199e61e4445..a3e7b390e0b 100644
--- a/appengine/standard/endpoints-frameworks-v2/echo/requirements-test.txt
+++ b/appengine/standard/endpoints-frameworks-v2/echo/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==4.6.11; python_version < '3.0'
-mock==3.0.5
+mock==3.0.5; python_version < '3.0'
diff --git a/appengine/standard/endpoints-frameworks-v2/quickstart/requirements-test.txt b/appengine/standard/endpoints-frameworks-v2/quickstart/requirements-test.txt
index 199e61e4445..a3e7b390e0b 100644
--- a/appengine/standard/endpoints-frameworks-v2/quickstart/requirements-test.txt
+++ b/appengine/standard/endpoints-frameworks-v2/quickstart/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==4.6.11; python_version < '3.0'
-mock==3.0.5
+mock==3.0.5; python_version < '3.0'
diff --git a/appengine/standard/firebase/firenotes/backend/requirements-test.txt b/appengine/standard/firebase/firenotes/backend/requirements-test.txt
index 199e61e4445..a3e7b390e0b 100644
--- a/appengine/standard/firebase/firenotes/backend/requirements-test.txt
+++ b/appengine/standard/firebase/firenotes/backend/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==4.6.11; python_version < '3.0'
-mock==3.0.5
+mock==3.0.5; python_version < '3.0'
diff --git a/appengine/standard/mailgun/requirements-test.txt b/appengine/standard/mailgun/requirements-test.txt
index edda954cce8..705d3b02103 100644
--- a/appengine/standard/mailgun/requirements-test.txt
+++ b/appengine/standard/mailgun/requirements-test.txt
@@ -1,4 +1,4 @@
 pytest==4.6.11; python_version < '3.0'
 google-api-python-client==1.9.3
-mock==3.0.5
+mock==3.0.5; python_version < '3.0'
 WebTest==2.0.35
diff --git a/appengine/standard/sendgrid/requirements-test.txt b/appengine/standard/sendgrid/requirements-test.txt
index c1b8f761b5a..774acfbd72d 100644
--- a/appengine/standard/sendgrid/requirements-test.txt
+++ b/appengine/standard/sendgrid/requirements-test.txt
@@ -1,3 +1,3 @@
 pytest==4.6.11; python_version < '3.0'
-mock==3.0.5
+mock==3.0.5; python_version < '3.0'
 WebTest==2.0.35
diff --git a/auth/api-client/requirements-test.txt b/auth/api-client/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/auth/api-client/requirements-test.txt
+++ b/auth/api-client/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/auth/cloud-client/requirements-test.txt b/auth/cloud-client/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/auth/cloud-client/requirements-test.txt
+++ b/auth/cloud-client/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/bigquery/cloud-client/requirements-test.txt b/bigquery/cloud-client/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/bigquery/cloud-client/requirements-test.txt
+++ b/bigquery/cloud-client/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/bigquery/pandas-gbq-migration/requirements-test.txt b/bigquery/pandas-gbq-migration/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/bigquery/pandas-gbq-migration/requirements-test.txt
+++ b/bigquery/pandas-gbq-migration/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/bigquery/transfer/cloud-client/requirements-test.txt b/bigquery/transfer/cloud-client/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/bigquery/transfer/cloud-client/requirements-test.txt
+++ b/bigquery/transfer/cloud-client/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/bigtable/metricscaler/requirements-test.txt b/bigtable/metricscaler/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/bigtable/metricscaler/requirements-test.txt
+++ b/bigtable/metricscaler/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/compute/auth/requirements-test.txt b/compute/auth/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/compute/auth/requirements-test.txt
+++ b/compute/auth/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/compute/metadata/requirements-test.txt b/compute/metadata/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/compute/metadata/requirements-test.txt
+++ b/compute/metadata/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/compute/oslogin/requirements-test.txt b/compute/oslogin/requirements-test.txt
index 1fe5e98f51f..5ac15be4116 100644
--- a/compute/oslogin/requirements-test.txt
+++ b/compute/oslogin/requirements-test.txt
@@ -1,3 +1,3 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
 retrying==1.3.3
diff --git a/dlp/requirements-test.txt b/dlp/requirements-test.txt
index 9a8c661f562..7cb2f0e3951 100644
--- a/dlp/requirements-test.txt
+++ b/dlp/requirements-test.txt
@@ -1,4 +1,4 @@
 pytest==5.4.3
 flaky==3.6.1
-mock==3.0.5
+mock==4.0.2
 
diff --git a/error_reporting/fluent_on_compute/requirements-test.txt b/error_reporting/fluent_on_compute/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/error_reporting/fluent_on_compute/requirements-test.txt
+++ b/error_reporting/fluent_on_compute/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/iot/api-client/gcs_file_to_device/requirements-test.txt b/iot/api-client/gcs_file_to_device/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/iot/api-client/gcs_file_to_device/requirements-test.txt
+++ b/iot/api-client/gcs_file_to_device/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/monitoring/api/v3/cloud-client/requirements-test.txt b/monitoring/api/v3/cloud-client/requirements-test.txt
index bf9b0ece710..94234b8fcf0 100644
--- a/monitoring/api/v3/cloud-client/requirements-test.txt
+++ b/monitoring/api/v3/cloud-client/requirements-test.txt
@@ -1,3 +1,3 @@
 backoff==1.10.0
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/run/image-processing/requirements-test.txt b/run/image-processing/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/run/image-processing/requirements-test.txt
+++ b/run/image-processing/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/spanner/cloud-client/requirements-test.txt b/spanner/cloud-client/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/spanner/cloud-client/requirements-test.txt
+++ b/spanner/cloud-client/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/speech/microphone/requirements-test.txt b/speech/microphone/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/speech/microphone/requirements-test.txt
+++ b/speech/microphone/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/storage/cloud-client/requirements-test.txt b/storage/cloud-client/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/storage/cloud-client/requirements-test.txt
+++ b/storage/cloud-client/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2
diff --git a/trace/cloud-trace-demo-app/app/requirements-test.txt b/trace/cloud-trace-demo-app/app/requirements-test.txt
index 1a71e3e3296..676ff949e8a 100644
--- a/trace/cloud-trace-demo-app/app/requirements-test.txt
+++ b/trace/cloud-trace-demo-app/app/requirements-test.txt
@@ -1,2 +1,2 @@
 pytest==5.4.3
-mock==3.0.5
+mock==4.0.2