diff --git a/README.md b/README.md
index 7a01286bfbe..15885178c2e 100644
--- a/README.md
+++ b/README.md
@@ -27,7 +27,7 @@ Network Policies in a very efficient manner.
 
 ## Prerequisites
 
-Antrea has been tested with Kubernetes clusters running version 1.16 or later.
+Antrea has been tested with Kubernetes clusters running version 1.19 or later.
 
 * `NodeIPAMController` must be enabled in the Kubernetes cluster.\
   When deploying a cluster with kubeadm the `--pod-network-cidr <cidr>`
diff --git a/build/charts/antrea/crds/clustergroup.yaml b/build/charts/antrea/crds/clustergroup.yaml
index 4ff7eaf5b9d..5d307e4fa8f 100644
--- a/build/charts/antrea/crds/clustergroup.yaml
+++ b/build/charts/antrea/crds/clustergroup.yaml
@@ -10,6 +10,8 @@ spec:
     - name: v1alpha3
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha3 ClusterGroup is deprecated; use crd.antrea.io/v1beta1 ClusterGroup"
       schema:
         openAPIV3Schema:
           type: object
diff --git a/build/charts/antrea/crds/clusternetworkpolicy.yaml b/build/charts/antrea/crds/clusternetworkpolicy.yaml
index a6e2cca2530..4880fed7b89 100644
--- a/build/charts/antrea/crds/clusternetworkpolicy.yaml
+++ b/build/charts/antrea/crds/clusternetworkpolicy.yaml
@@ -10,6 +10,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 ClusterNetworkPolicy is deprecated; use crd.antrea.io/v1beta1 ClusterNetworkPolicy"
       additionalPrinterColumns:
         - name: Tier
           type: string
diff --git a/build/charts/antrea/crds/externalippool.yaml b/build/charts/antrea/crds/externalippool.yaml
index ac17a519c1b..91ae909b0d6 100644
--- a/build/charts/antrea/crds/externalippool.yaml
+++ b/build/charts/antrea/crds/externalippool.yaml
@@ -10,6 +10,8 @@ spec:
     - name: v1alpha2
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha2 ExternalIPPool is deprecated; use crd.antrea.io/v1beta1 ExternalIPPool"
       schema:
         openAPIV3Schema:
           type: object
diff --git a/build/charts/antrea/crds/group.yaml b/build/charts/antrea/crds/group.yaml
index a39783a7b57..e9dd998a243 100644
--- a/build/charts/antrea/crds/group.yaml
+++ b/build/charts/antrea/crds/group.yaml
@@ -8,6 +8,8 @@ spec:
     - name: v1alpha3
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha3 Group is deprecated; use crd.antrea.io/v1beta1 Group"
       schema:
         openAPIV3Schema:
           type: object
diff --git a/build/charts/antrea/crds/networkpolicy.yaml b/build/charts/antrea/crds/networkpolicy.yaml
index f9b281dd97a..abc84a58c1e 100644
--- a/build/charts/antrea/crds/networkpolicy.yaml
+++ b/build/charts/antrea/crds/networkpolicy.yaml
@@ -10,6 +10,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 NetworkPolicy is deprecated; use crd.antrea.io/v1beta1 NetworkPolicy"
       additionalPrinterColumns:
         - name: Tier
           type: string
diff --git a/build/charts/antrea/crds/traceflow.yaml b/build/charts/antrea/crds/traceflow.yaml
index 90b139ecb4f..72a1f99fa95 100644
--- a/build/charts/antrea/crds/traceflow.yaml
+++ b/build/charts/antrea/crds/traceflow.yaml
@@ -10,6 +10,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 Traceflow is deprecated; use crd.antrea.io/v1beta1 Traceflow"
       additionalPrinterColumns:
         - jsonPath: .status.phase
           description: The phase of the Traceflow.
diff --git a/build/yamls/antrea-aks.yml b/build/yamls/antrea-aks.yml
index a2cd0b827d2..dc1dca6afaf 100644
--- a/build/yamls/antrea-aks.yml
+++ b/build/yamls/antrea-aks.yml
@@ -314,6 +314,8 @@ spec:
     - name: v1alpha3
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha3 ClusterGroup is deprecated; use crd.antrea.io/v1beta1 ClusterGroup"
       schema:
         openAPIV3Schema:
           type: object
@@ -576,6 +578,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 ClusterNetworkPolicy is deprecated; use crd.antrea.io/v1beta1 ClusterNetworkPolicy"
       additionalPrinterColumns:
         - name: Tier
           type: string
@@ -2406,6 +2410,8 @@ spec:
     - name: v1alpha2
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha2 ExternalIPPool is deprecated; use crd.antrea.io/v1beta1 ExternalIPPool"
       schema:
         openAPIV3Schema:
           type: object
@@ -2671,6 +2677,8 @@ spec:
     - name: v1alpha3
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha3 Group is deprecated; use crd.antrea.io/v1beta1 Group"
       schema:
         openAPIV3Schema:
           type: object
@@ -3052,6 +3060,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 NetworkPolicy is deprecated; use crd.antrea.io/v1beta1 NetworkPolicy"
       additionalPrinterColumns:
         - name: Tier
           type: string
@@ -4515,6 +4525,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 Traceflow is deprecated; use crd.antrea.io/v1beta1 Traceflow"
       additionalPrinterColumns:
         - jsonPath: .status.phase
           description: The phase of the Traceflow.
diff --git a/build/yamls/antrea-crds.yml b/build/yamls/antrea-crds.yml
index 8864d50ba06..a98db47935c 100644
--- a/build/yamls/antrea-crds.yml
+++ b/build/yamls/antrea-crds.yml
@@ -309,6 +309,8 @@ spec:
     - name: v1alpha3
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha3 ClusterGroup is deprecated; use crd.antrea.io/v1beta1 ClusterGroup"
       schema:
         openAPIV3Schema:
           type: object
@@ -569,6 +571,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 ClusterNetworkPolicy is deprecated; use crd.antrea.io/v1beta1 ClusterNetworkPolicy"
       additionalPrinterColumns:
         - name: Tier
           type: string
@@ -2393,6 +2397,8 @@ spec:
     - name: v1alpha2
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha2 ExternalIPPool is deprecated; use crd.antrea.io/v1beta1 ExternalIPPool"
       schema:
         openAPIV3Schema:
           type: object
@@ -2654,6 +2660,8 @@ spec:
     - name: v1alpha3
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha3 Group is deprecated; use crd.antrea.io/v1beta1 Group"
       schema:
         openAPIV3Schema:
           type: object
@@ -3031,6 +3039,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 NetworkPolicy is deprecated; use crd.antrea.io/v1beta1 NetworkPolicy"
       additionalPrinterColumns:
         - name: Tier
           type: string
@@ -4488,6 +4498,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 Traceflow is deprecated; use crd.antrea.io/v1beta1 Traceflow"
       additionalPrinterColumns:
         - jsonPath: .status.phase
           description: The phase of the Traceflow.
diff --git a/build/yamls/antrea-eks.yml b/build/yamls/antrea-eks.yml
index b47cd651b64..899d6c16192 100644
--- a/build/yamls/antrea-eks.yml
+++ b/build/yamls/antrea-eks.yml
@@ -314,6 +314,8 @@ spec:
     - name: v1alpha3
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha3 ClusterGroup is deprecated; use crd.antrea.io/v1beta1 ClusterGroup"
       schema:
         openAPIV3Schema:
           type: object
@@ -576,6 +578,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 ClusterNetworkPolicy is deprecated; use crd.antrea.io/v1beta1 ClusterNetworkPolicy"
       additionalPrinterColumns:
         - name: Tier
           type: string
@@ -2406,6 +2410,8 @@ spec:
     - name: v1alpha2
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha2 ExternalIPPool is deprecated; use crd.antrea.io/v1beta1 ExternalIPPool"
       schema:
         openAPIV3Schema:
           type: object
@@ -2671,6 +2677,8 @@ spec:
     - name: v1alpha3
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha3 Group is deprecated; use crd.antrea.io/v1beta1 Group"
       schema:
         openAPIV3Schema:
           type: object
@@ -3052,6 +3060,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 NetworkPolicy is deprecated; use crd.antrea.io/v1beta1 NetworkPolicy"
       additionalPrinterColumns:
         - name: Tier
           type: string
@@ -4515,6 +4525,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 Traceflow is deprecated; use crd.antrea.io/v1beta1 Traceflow"
       additionalPrinterColumns:
         - jsonPath: .status.phase
           description: The phase of the Traceflow.
diff --git a/build/yamls/antrea-gke.yml b/build/yamls/antrea-gke.yml
index 0984ab8ff54..69b9be4f36a 100644
--- a/build/yamls/antrea-gke.yml
+++ b/build/yamls/antrea-gke.yml
@@ -314,6 +314,8 @@ spec:
     - name: v1alpha3
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha3 ClusterGroup is deprecated; use crd.antrea.io/v1beta1 ClusterGroup"
       schema:
         openAPIV3Schema:
           type: object
@@ -576,6 +578,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 ClusterNetworkPolicy is deprecated; use crd.antrea.io/v1beta1 ClusterNetworkPolicy"
       additionalPrinterColumns:
         - name: Tier
           type: string
@@ -2406,6 +2410,8 @@ spec:
     - name: v1alpha2
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha2 ExternalIPPool is deprecated; use crd.antrea.io/v1beta1 ExternalIPPool"
       schema:
         openAPIV3Schema:
           type: object
@@ -2671,6 +2677,8 @@ spec:
     - name: v1alpha3
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha3 Group is deprecated; use crd.antrea.io/v1beta1 Group"
       schema:
         openAPIV3Schema:
           type: object
@@ -3052,6 +3060,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 NetworkPolicy is deprecated; use crd.antrea.io/v1beta1 NetworkPolicy"
       additionalPrinterColumns:
         - name: Tier
           type: string
@@ -4515,6 +4525,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 Traceflow is deprecated; use crd.antrea.io/v1beta1 Traceflow"
       additionalPrinterColumns:
         - jsonPath: .status.phase
           description: The phase of the Traceflow.
diff --git a/build/yamls/antrea-ipsec.yml b/build/yamls/antrea-ipsec.yml
index 1da6e0b3e27..b4b258bf3f2 100644
--- a/build/yamls/antrea-ipsec.yml
+++ b/build/yamls/antrea-ipsec.yml
@@ -314,6 +314,8 @@ spec:
     - name: v1alpha3
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha3 ClusterGroup is deprecated; use crd.antrea.io/v1beta1 ClusterGroup"
       schema:
         openAPIV3Schema:
           type: object
@@ -576,6 +578,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 ClusterNetworkPolicy is deprecated; use crd.antrea.io/v1beta1 ClusterNetworkPolicy"
       additionalPrinterColumns:
         - name: Tier
           type: string
@@ -2406,6 +2410,8 @@ spec:
     - name: v1alpha2
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha2 ExternalIPPool is deprecated; use crd.antrea.io/v1beta1 ExternalIPPool"
       schema:
         openAPIV3Schema:
           type: object
@@ -2671,6 +2677,8 @@ spec:
     - name: v1alpha3
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha3 Group is deprecated; use crd.antrea.io/v1beta1 Group"
       schema:
         openAPIV3Schema:
           type: object
@@ -3052,6 +3060,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 NetworkPolicy is deprecated; use crd.antrea.io/v1beta1 NetworkPolicy"
       additionalPrinterColumns:
         - name: Tier
           type: string
@@ -4515,6 +4525,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 Traceflow is deprecated; use crd.antrea.io/v1beta1 Traceflow"
       additionalPrinterColumns:
         - jsonPath: .status.phase
           description: The phase of the Traceflow.
diff --git a/build/yamls/antrea.yml b/build/yamls/antrea.yml
index e3d12af05e1..b8a1c6b6ad2 100644
--- a/build/yamls/antrea.yml
+++ b/build/yamls/antrea.yml
@@ -314,6 +314,8 @@ spec:
     - name: v1alpha3
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha3 ClusterGroup is deprecated; use crd.antrea.io/v1beta1 ClusterGroup"
       schema:
         openAPIV3Schema:
           type: object
@@ -576,6 +578,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 ClusterNetworkPolicy is deprecated; use crd.antrea.io/v1beta1 ClusterNetworkPolicy"
       additionalPrinterColumns:
         - name: Tier
           type: string
@@ -2406,6 +2410,8 @@ spec:
     - name: v1alpha2
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha2 ExternalIPPool is deprecated; use crd.antrea.io/v1beta1 ExternalIPPool"
       schema:
         openAPIV3Schema:
           type: object
@@ -2671,6 +2677,8 @@ spec:
     - name: v1alpha3
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha3 Group is deprecated; use crd.antrea.io/v1beta1 Group"
       schema:
         openAPIV3Schema:
           type: object
@@ -3052,6 +3060,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 NetworkPolicy is deprecated; use crd.antrea.io/v1beta1 NetworkPolicy"
       additionalPrinterColumns:
         - name: Tier
           type: string
@@ -4515,6 +4525,8 @@ spec:
     - name: v1alpha1
       served: true
       storage: false
+      deprecated: true
+      deprecationWarning: "crd.antrea.io/v1alpha1 Traceflow is deprecated; use crd.antrea.io/v1beta1 Traceflow"
       additionalPrinterColumns:
         - jsonPath: .status.phase
           description: The phase of the Traceflow.
diff --git a/pkg/apiserver/handlers/webhook/convert_crd.go b/pkg/apiserver/handlers/webhook/convert_crd.go
index 930789bd525..eec3d16baa1 100644
--- a/pkg/apiserver/handlers/webhook/convert_crd.go
+++ b/pkg/apiserver/handlers/webhook/convert_crd.go
@@ -45,6 +45,7 @@ func statusSucceed() metav1.Status {
 
 // doConversionV1beta1 converts the requested objects in the v1beta1 ConversionRequest using the given conversion function and
 // returns a conversion response. Failures are reported with the Reason in the conversion response.
+// Deprecated: apiextensions/v1beta1 is deprecated, use apiextensions/v1 instead
 func doConversionV1beta1(convertRequest *v1beta1.ConversionRequest, convert convertFunc) *v1beta1.ConversionResponse {
 	var convertedObjects []runtime.RawExtension
 	for _, obj := range convertRequest.Objects {