diff --git a/IMPLEMENTATION_COVERAGE.md b/IMPLEMENTATION_COVERAGE.md
index 6e6a13c35..4646e8a6c 100644
--- a/IMPLEMENTATION_COVERAGE.md
+++ b/IMPLEMENTATION_COVERAGE.md
@@ -2376,11 +2376,11 @@
 - [ ] unsubscribe_from_event
 - [ ] update_assessment_target
 
-## iot - 30% implemented
+## iot - 32% implemented
 - [ ] accept_certificate_transfer
 - [X] add_thing_to_thing_group
 - [ ] associate_targets_with_job
-- [ ] attach_policy
+- [X] attach_policy
 - [X] attach_principal_policy
 - [X] attach_thing_principal
 - [ ] cancel_certificate_transfer
@@ -2429,7 +2429,7 @@
 - [X] describe_thing_group
 - [ ] describe_thing_registration_task
 - [X] describe_thing_type
-- [ ] detach_policy
+- [X] detach_policy
 - [X] detach_principal_policy
 - [X] detach_thing_principal
 - [ ] disable_topic_rule
diff --git a/moto/iot/models.py b/moto/iot/models.py
index 4b0b260e1..b493f6b8d 100644
--- a/moto/iot/models.py
+++ b/moto/iot/models.py
@@ -457,6 +457,14 @@ class IoTBackend(BaseBackend):
             pass
         raise ResourceNotFoundException()
 
+    def attach_policy(self, policy_name, target):
+        principal = self._get_principal(target)
+        policy = self.get_policy(policy_name)
+        k = (target, policy_name)
+        if k in self.principal_policies:
+            return
+        self.principal_policies[k] = (principal, policy)
+
     def attach_principal_policy(self, policy_name, principal_arn):
         principal = self._get_principal(principal_arn)
         policy = self.get_policy(policy_name)
@@ -465,6 +473,15 @@ class IoTBackend(BaseBackend):
             return
         self.principal_policies[k] = (principal, policy)
 
+    def detach_policy(self, policy_name, target):
+        # this may raises ResourceNotFoundException
+        self._get_principal(target)
+        self.get_policy(policy_name)
+        k = (target, policy_name)
+        if k not in self.principal_policies:
+            raise ResourceNotFoundException()
+        del self.principal_policies[k]
+
     def detach_principal_policy(self, policy_name, principal_arn):
         # this may raises ResourceNotFoundException
         self._get_principal(principal_arn)
diff --git a/moto/iot/responses.py b/moto/iot/responses.py
index 006c4c4cc..214576f52 100644
--- a/moto/iot/responses.py
+++ b/moto/iot/responses.py
@@ -224,6 +224,15 @@ class IoTResponse(BaseResponse):
         )
         return json.dumps(dict())
 
+    def attach_policy(self):
+        policy_name = self._get_param("policyName")
+        target = self._get_param('target')
+        self.iot_backend.attach_policy(
+            policy_name=policy_name,
+            target=target,
+        )
+        return json.dumps(dict())
+
     def attach_principal_policy(self):
         policy_name = self._get_param("policyName")
         principal = self.headers.get('x-amzn-iot-principal')
@@ -233,6 +242,15 @@ class IoTResponse(BaseResponse):
         )
         return json.dumps(dict())
 
+    def detach_policy(self):
+        policy_name = self._get_param("policyName")
+        target = self._get_param('target')
+        self.iot_backend.detach_policy(
+            policy_name=policy_name,
+            target=target,
+        )
+        return json.dumps(dict())
+
     def detach_principal_policy(self):
         policy_name = self._get_param("policyName")
         principal = self.headers.get('x-amzn-iot-principal')
diff --git a/tests/test_iot/test_iot.py b/tests/test_iot/test_iot.py
index 21b670d46..826d2c56b 100644
--- a/tests/test_iot/test_iot.py
+++ b/tests/test_iot/test_iot.py
@@ -401,6 +401,47 @@ def test_policy():
 
 @mock_iot
 def test_principal_policy():
+    client = boto3.client('iot', region_name='ap-northeast-1')
+    policy_name = 'my-policy'
+    doc = '{}'
+    client.create_policy(policyName=policy_name, policyDocument=doc)
+    cert = client.create_keys_and_certificate(setAsActive=True)
+    cert_arn = cert['certificateArn']
+
+    client.attach_policy(policyName=policy_name, target=cert_arn)
+
+    res = client.list_principal_policies(principal=cert_arn)
+    res.should.have.key('policies').which.should.have.length_of(1)
+    for policy in res['policies']:
+        policy.should.have.key('policyName').which.should_not.be.none
+        policy.should.have.key('policyArn').which.should_not.be.none
+
+    # do nothing if policy have already attached to certificate
+    client.attach_policy(policyName=policy_name, target=cert_arn)
+
+    res = client.list_principal_policies(principal=cert_arn)
+    res.should.have.key('policies').which.should.have.length_of(1)
+    for policy in res['policies']:
+        policy.should.have.key('policyName').which.should_not.be.none
+        policy.should.have.key('policyArn').which.should_not.be.none
+
+    res = client.list_policy_principals(policyName=policy_name)
+    res.should.have.key('principals').which.should.have.length_of(1)
+    for principal in res['principals']:
+        principal.should_not.be.none
+
+    client.detach_policy(policyName=policy_name, target=cert_arn)
+    res = client.list_principal_policies(principal=cert_arn)
+    res.should.have.key('policies').which.should.have.length_of(0)
+    res = client.list_policy_principals(policyName=policy_name)
+    res.should.have.key('principals').which.should.have.length_of(0)
+    with assert_raises(ClientError) as e:
+        client.detach_policy(policyName=policy_name, target=cert_arn)
+    e.exception.response['Error']['Code'].should.equal('ResourceNotFoundException')
+
+
+@mock_iot
+def test_principal_policy_deprecated():
     client = boto3.client('iot', region_name='ap-northeast-1')
     policy_name = 'my-policy'
     doc = '{}'