diff --git a/src/azure-cli/azure/cli/command_modules/acs/managed_cluster_decorator.py b/src/azure-cli/azure/cli/command_modules/acs/managed_cluster_decorator.py
index 0cbafafdb37..988f9ade01b 100644
--- a/src/azure-cli/azure/cli/command_modules/acs/managed_cluster_decorator.py
+++ b/src/azure-cli/azure/cli/command_modules/acs/managed_cluster_decorator.py
@@ -4706,17 +4706,13 @@ def get_k8s_support_plan(self) -> Union[str, None]:
 
         :return: string or None
         """
-        # default to None
-        support_plan = None
-        # try to read the property value corresponding to the parameter from the `mc` object
-        if self.mc and hasattr(self.mc, "support_plan") and self.mc.support_plan is not None:
-            support_plan = self.mc.support_plan
-
-        # if specified by customer, use the specified value
+        # take input
         support_plan = self.raw_param.get("k8s_support_plan")
+        if support_plan is None:
+            # user didn't update this property, load from existing ManagedCluster
+            if self.mc and hasattr(self.mc, "support_plan") and self.mc.support_plan is not None:
+                support_plan = self.mc.support_plan
 
-        # this parameter does not need dynamic completion
-        # this parameter does not need validation
         return support_plan
 
     def get_yes(self) -> bool:
diff --git a/src/azure-cli/azure/cli/command_modules/acs/tests/latest/test_managed_cluster_decorator.py b/src/azure-cli/azure/cli/command_modules/acs/tests/latest/test_managed_cluster_decorator.py
index a27d4f04549..6f7ec16dc28 100644
--- a/src/azure-cli/azure/cli/command_modules/acs/tests/latest/test_managed_cluster_decorator.py
+++ b/src/azure-cli/azure/cli/command_modules/acs/tests/latest/test_managed_cluster_decorator.py
@@ -10467,5 +10467,116 @@ def test_update_http_proxy_config(self):
         )
         self.assertEqual(dec_mc_1, ground_truth_mc_1)
 
+    def test_setup_supportPlan(self):
+        # default value in `aks_create`
+        ltsDecorator = AKSManagedClusterCreateDecorator(
+            self.cmd,
+            self.client,
+            {
+                "k8s_support_plan": "AKSLongTermSupport"
+            },
+            ResourceType.MGMT_CONTAINERSERVICE,
+        )
+
+        premiumSKU = self.models.ManagedClusterSKU(
+                name="Base",
+                tier="Premium")
+        premiumCluster = self.models.ManagedCluster(
+            location="test_location", 
+            support_plan=None,
+            sku=premiumSKU,
+        )
+        ltsDecorator.context.attach_mc(premiumCluster)
+
+        # fail on passing the wrong mc object
+        with self.assertRaises(CLIInternalError):
+            ltsDecorator.set_up_k8s_support_plan(None)
+
+        ltsClusterCalculated = ltsDecorator.set_up_k8s_support_plan(premiumCluster)
+        expectedLTSCluster = self.models.ManagedCluster(
+            location="test_location",
+            support_plan="AKSLongTermSupport",
+            sku=premiumSKU,
+        )
+        self.assertEqual(ltsClusterCalculated, expectedLTSCluster)
+
+        nonLTSDecorator = AKSManagedClusterCreateDecorator(
+            self.cmd,
+            self.client,
+            {
+                "k8s_support_plan": "KubernetesOfficial"
+            },
+            ResourceType.MGMT_CONTAINERSERVICE,
+        )
+        nonLTSDecorator.context.attach_mc(premiumCluster)
+        nonLTSClusterCalculated = nonLTSDecorator.set_up_k8s_support_plan(premiumCluster)
+        expectedNonLTSCluster = self.models.ManagedCluster(
+            location="test_location",
+            support_plan="KubernetesOfficial",
+            sku=premiumSKU,
+        )
+        self.assertEqual(nonLTSClusterCalculated, expectedNonLTSCluster)
+
+    def test_update_supportPlan(self):
+        # default value in `aks_create`
+        noopDecorator = AKSManagedClusterUpdateDecorator(
+            self.cmd,
+            self.client,
+            {},
+            ResourceType.MGMT_CONTAINERSERVICE,
+        )
+
+        premiumSKU = self.models.ManagedClusterSKU(
+                name="Base",
+                tier="Premium")
+        ltsCluster = self.models.ManagedCluster(
+            location="test_location", 
+            sku=premiumSKU,
+            support_plan="AKSLongTermSupport",
+        )
+        noopDecorator.context.attach_mc(ltsCluster)
+
+        # fail on passing the wrong mc object
+        with self.assertRaises(CLIInternalError):
+            noopDecorator.update_k8s_support_plan(None)
+
+        ltsClusterCalculated = noopDecorator.update_k8s_support_plan(ltsCluster)
+        self.assertEqual(ltsClusterCalculated, ltsCluster)
+
+        disableLTSDecorator = AKSManagedClusterUpdateDecorator(
+            self.cmd,
+            self.client,
+            {
+                "k8s_support_plan": "KubernetesOfficial"
+            },
+            ResourceType.MGMT_CONTAINERSERVICE,
+        )
+        disableLTSDecorator.context.attach_mc(ltsCluster)
+        nonLTSClusterCalculated = disableLTSDecorator.update_k8s_support_plan(ltsCluster)
+        expectedNonLTSCluster = self.models.ManagedCluster(
+            location="test_location",
+            support_plan="KubernetesOfficial",
+            sku=premiumSKU,
+        )
+        self.assertEqual(nonLTSClusterCalculated, expectedNonLTSCluster)
+
+        normalCluster = self.models.ManagedCluster(
+            location="test_location", 
+            sku=self.models.ManagedClusterSKU(
+                name="Base",
+                tier="Standard"),
+            support_plan="KubernetesOfficial",
+        )
+        noopDecorator3 = AKSManagedClusterUpdateDecorator(
+            self.cmd,
+            self.client,
+            {},
+            ResourceType.MGMT_CONTAINERSERVICE,
+        )
+        noopDecorator3.context.attach_mc(normalCluster)
+        normalClusterCalculated = noopDecorator3.update_k8s_support_plan(normalCluster)
+        self.assertEqual(normalClusterCalculated, normalCluster)
+
+
 if __name__ == "__main__":
     unittest.main()