diff --git a/src/azure-cli/azure/cli/command_modules/acs/_params.py b/src/azure-cli/azure/cli/command_modules/acs/_params.py
index dea20bf437c..206bb782a6b 100644
--- a/src/azure-cli/azure/cli/command_modules/acs/_params.py
+++ b/src/azure-cli/azure/cli/command_modules/acs/_params.py
@@ -595,7 +595,8 @@ def load_arguments(self, _):
 
         # nodepool paramerters
         c.argument('nodepool_name', default='nodepool1',
-                   help='Node pool name, up to 12 alphanumeric characters', validator=validate_nodepool_name)
+                   help='Node pool name, alphanumeric characters only. '
+                   'See https://aka.ms/aks-naming-rules for length limits.', validator=validate_nodepool_name)
         c.argument('node_vm_size', options_list=['--node-vm-size', '-s'])
         c.argument('vm_sizes')
         c.argument('os_sku', arg_type=get_enum_type(node_os_skus_create), validator=validate_os_sku)
@@ -1155,7 +1156,9 @@ def load_arguments(self, _):
         c.argument("tier", arg_type=get_enum_type(sku_tiers), validator=validate_sku_tier)
 
     with self.argument_context('aks scale', resource_type=ResourceType.MGMT_CONTAINERSERVICE, operation_group='managed_clusters') as c:
-        c.argument('nodepool_name', validator=validate_nodepool_name, help='Node pool name, up to 12 alphanumeric characters.')
+        c.argument('nodepool_name', validator=validate_nodepool_name,
+                   help='Node pool name, alphanumeric characters only. '
+                   'See https://aka.ms/aks-naming-rules for length limits.')
 
     # managed namespace
     with self.argument_context("aks namespace") as c:
diff --git a/src/azure-cli/azure/cli/command_modules/acs/_validators.py b/src/azure-cli/azure/cli/command_modules/acs/_validators.py
index bab4888fc5f..4dc32d9238c 100644
--- a/src/azure-cli/azure/cli/command_modules/acs/_validators.py
+++ b/src/azure-cli/azure/cli/command_modules/acs/_validators.py
@@ -184,21 +184,21 @@ def validate_k8s_version(namespace):
 
 
 def _validate_nodepool_name(nodepool_name):
-    """Validates a nodepool name to be at most 12 characters, alphanumeric only."""
+    """Validates a nodepool name to be at most 39 characters, alphanumeric only."""
     if nodepool_name != "":
-        if len(nodepool_name) > 12:
-            raise InvalidArgumentValueError('--nodepool-name can contain at most 12 characters')
+        if len(nodepool_name) > 39:
+            raise InvalidArgumentValueError('--nodepool-name can contain at most 39 characters')
         if not nodepool_name.isalnum():
             raise InvalidArgumentValueError('--nodepool-name should contain only alphanumeric characters')
 
 
 def validate_nodepool_name(namespace):
-    """Validates a nodepool name to be at most 12 characters, alphanumeric only."""
+    """Validates a nodepool name to be at most 39 characters, alphanumeric only."""
     _validate_nodepool_name(namespace.nodepool_name)
 
 
 def validate_agent_pool_name(namespace):
-    """Validates a nodepool name to be at most 12 characters, alphanumeric only."""
+    """Validates a nodepool name to be at most 39 characters, alphanumeric only."""
     _validate_nodepool_name(namespace.agent_pool_name)
 
 
diff --git a/src/azure-cli/azure/cli/command_modules/acs/tests/latest/test_validators.py b/src/azure-cli/azure/cli/command_modules/acs/tests/latest/test_validators.py
index f84f4e107ad..3640e3848c1 100644
--- a/src/azure-cli/azure/cli/command_modules/acs/tests/latest/test_validators.py
+++ b/src/azure-cli/azure/cli/command_modules/acs/tests/latest/test_validators.py
@@ -725,10 +725,10 @@ class TestValidateNodepoolName(unittest.TestCase):
     def test_invalid_nodepool_name_too_long(self):
         namespace = SimpleNamespace(
             **{
-                "nodepool_name": "tooLongNodepoolName",
+                "nodepool_name": "a" * 40,
             }
         )
-        with self.assertRaises(InvalidArgumentValueError):
+        with self.assertRaisesRegex(InvalidArgumentValueError, "at most 39 characters"):
             validators.validate_nodepool_name(
                 namespace
             )
@@ -736,10 +736,10 @@ def test_invalid_nodepool_name_too_long(self):
     def test_invalid_agent_pool_name_too_long(self):
         namespace = SimpleNamespace(
             **{
-                "agent_pool_name": "tooLongNodepoolName",
+                "agent_pool_name": "a" * 40,
             }
         )
-        with self.assertRaises(InvalidArgumentValueError):
+        with self.assertRaisesRegex(InvalidArgumentValueError, "at most 39 characters"):
             validators.validate_agent_pool_name(
                 namespace
             )
@@ -786,6 +786,24 @@ def test_valid_agent_pool_name(self):
             namespace
         )
 
+    def test_valid_nodepool_name_length_boundaries(self):
+        for length in (12, 13, 39):
+            with self.subTest(length=length):
+                namespace = SimpleNamespace(nodepool_name="a" * length)
+                validators.validate_nodepool_name(namespace)
+
+    def test_valid_agent_pool_name_length_boundaries(self):
+        for length in (12, 13, 39):
+            with self.subTest(length=length):
+                namespace = SimpleNamespace(agent_pool_name="a" * length)
+                validators.validate_agent_pool_name(namespace)
+
+    def test_valid_empty_nodepool_name(self):
+        validators.validate_nodepool_name(SimpleNamespace(nodepool_name=""))
+
+    def test_valid_empty_agent_pool_name(self):
+        validators.validate_agent_pool_name(SimpleNamespace(agent_pool_name=""))
+
 
 class GatewayPrefixSizeSpace:
     def __init__(self, gateway_prefix_size=None, mode=None):