diff --git a/README.md b/README.md
index 89cae268..607bc897 100644
--- a/README.md
+++ b/README.md
@@ -149,9 +149,6 @@ This is a helper script for Knative E2E test scripts. To use it:
 1. By default `knative_teardown()` and `test_teardown()` will be called after
    the tests finish, use `--skip-teardowns` if you don't want them to be called.
 
-1. By default Istio is installed on the cluster via Addon, use
-   `--skip-istio-addon` if you choose not to have it preinstalled.
-
 1. By default Google Kubernetes Engine telemetry to Cloud Logging and Monitoring is disabled.
    This can be enabled by setting `ENABLE_GKE_TELEMETRY` to `true`.
    
diff --git a/e2e-tests.sh b/e2e-tests.sh
index 77c01eca..cb186a4e 100755
--- a/e2e-tests.sh
+++ b/e2e-tests.sh
@@ -98,9 +98,6 @@ function setup_test_cluster() {
   set +o errexit
   set +o pipefail
 
-  # Wait for Istio installation to complete, if necessary, before calling knative_setup.
-  # TODO(chizhg): is it really needed?
-  (( ! SKIP_ISTIO_ADDON )) && (wait_until_batch_job_complete istio-system || return 1)
   if function_exists knative_setup; then
     knative_setup || fail_test "Knative setup failed"
   fi
@@ -130,7 +127,6 @@ function fail_test() {
 }
 
 SKIP_TEARDOWNS=0
-SKIP_ISTIO_ADDON=0
 E2E_SCRIPT=""
 CLOUD_PROVIDER="gke"
 
@@ -170,8 +166,8 @@ function initialize() {
     case ${parameter} in
       --run-tests) run_tests=1 ;;
       --skip-teardowns) SKIP_TEARDOWNS=1 ;;
-      # TODO(chizhg): remove this flag once the addons is defined as an env var.
-      --skip-istio-addon) SKIP_ISTIO_ADDON=1 ;;
+      --skip-istio-addon) echo "--skip-istio-addon is no longer supported"
+        ;; # This flag is a noop
       *)
         case ${parameter} in
           --cloud-provider) shift; CLOUD_PROVIDER="$1" ;;
@@ -184,11 +180,7 @@ function initialize() {
   (( IS_PROW )) && [[ -z "${GCP_PROJECT_ID:-}" ]] && IS_BOSKOS=1
 
   if [[ "${CLOUD_PROVIDER}" == "gke" ]]; then
-    if (( SKIP_ISTIO_ADDON )); then
       custom_flags+=("--addons=NodeLocalDNS")
-    else
-      custom_flags+=("--addons=Istio,NodeLocalDNS")
-    fi
   fi
 
   readonly IS_BOSKOS
diff --git a/test/unit/presubmit_test.go b/test/unit/presubmit_test.go
index 8bd80fc3..5d26d23a 100644
--- a/test/unit/presubmit_test.go
+++ b/test/unit/presubmit_test.go
@@ -53,7 +53,7 @@ func TestMainFunc(t *testing.T) {
 				"--enable-workload-identity --cluster-version=latest "+
 				"--extra-gcloud-flags --enable-stackdriver-kubernetes "+
 				"--no-enable-ip-alias --no-enable-autoupgrade "+
-				"--addons=Istio,NodeLocalDNS "+
+				"--addons=NodeLocalDNS "+
 				"--test-command=%s/test/e2e-tests.sh "+
 				"--run-tests --extra-gcloud-flags= --logging=NONE "+
 				"--monitoring=NONE", rootDir)),
diff --git a/test/unit/run_e2e_test.go b/test/unit/run_e2e_test.go
index 34643b8e..01d13e44 100644
--- a/test/unit/run_e2e_test.go
+++ b/test/unit/run_e2e_test.go
@@ -15,7 +15,6 @@ func TestRunE2eTests(t *testing.T) {
 		stdout: []check{
 			contains("SETTING UP TEST CLUSTER"),
 			contains("Cluster is gke_deadbeef_1.24"),
-			contains("kubectl wait job --for=condition=Complete --all -n istio-system --timeout=5m"),
 			contains("STARTING KNATIVE SERVING"),
 			contains("Waiting until all pods in namespace knative-serving are up"),
 			contains("E2E TESTS PASSED"),