diff --git a/IMPLEMENTATION_COVERAGE.md b/IMPLEMENTATION_COVERAGE.md
index 498910222..dc27017d2 100644
--- a/IMPLEMENTATION_COVERAGE.md
+++ b/IMPLEMENTATION_COVERAGE.md
@@ -6740,9 +6740,9 @@
 <details>
 <summary>29% implemented</summary>
 
-- [ ] add_flow_outputs
+- [X] add_flow_outputs
 - [ ] add_flow_sources
-- [ ] add_flow_vpc_interfaces
+- [X] add_flow_vpc_interfaces
 - [X] create_flow
 - [X] delete_flow
 - [X] describe_flow
diff --git a/moto/mediaconnect/models.py b/moto/mediaconnect/models.py
index ae4b16578..a48f42e8d 100644
--- a/moto/mediaconnect/models.py
+++ b/moto/mediaconnect/models.py
@@ -185,6 +185,26 @@ class MediaConnectBackend(BaseBackend):
             raise NotFoundException(message="Resource not found.")
         return resource.tags
 
+    def add_flow_vpc_interfaces(self, flow_arn, vpc_interfaces):
+        if flow_arn in self._flows:
+            flow = self._flows[flow_arn]
+            flow.vpc_interfaces = vpc_interfaces
+        else:
+            raise NotFoundException(
+                message="flow with arn={} not found".format(flow_arn)
+            )
+        return flow_arn, flow.vpc_interfaces
+
+    def add_flow_outputs(self, flow_arn, outputs):
+        if flow_arn in self._flows:
+            flow = self._flows[flow_arn]
+            flow.outputs = outputs
+        else:
+            raise NotFoundException(
+                message="flow with arn={} not found".format(flow_arn)
+            )
+        return flow_arn, flow.outputs
+
     # add methods from here
 
 
diff --git a/moto/mediaconnect/responses.py b/moto/mediaconnect/responses.py
index 9b6e2c155..495463f98 100644
--- a/moto/mediaconnect/responses.py
+++ b/moto/mediaconnect/responses.py
@@ -81,3 +81,21 @@ class MediaConnectResponse(BaseResponse):
             resource_arn=resource_arn,
         )
         return json.dumps(dict(tags=tags))
+
+    def add_flow_vpc_interfaces(self):
+        flow_arn = unquote(self._get_param("flowArn"))
+        vpc_interfaces = self._get_param("vpcInterfaces")
+        flow_arn, vpc_interfaces = self.mediaconnect_backend.add_flow_vpc_interfaces(
+            flow_arn=flow_arn, vpc_interfaces=vpc_interfaces
+        )
+        return json.dumps(dict(flow_arn=flow_arn, vpc_interfaces=vpc_interfaces))
+
+    def add_flow_outputs(self):
+        flow_arn = unquote(self._get_param("flowArn"))
+        outputs = self._get_param("outputs")
+        flow_arn, outputs = self.mediaconnect_backend.add_flow_outputs(
+            flow_arn=flow_arn, outputs=outputs
+        )
+        return json.dumps(dict(flow_arn=flow_arn, outputs=outputs))
+
+    # add methods from here
diff --git a/moto/mediaconnect/urls.py b/moto/mediaconnect/urls.py
index dc66635b7..c5b5dfc1a 100644
--- a/moto/mediaconnect/urls.py
+++ b/moto/mediaconnect/urls.py
@@ -12,6 +12,8 @@ response = MediaConnectResponse()
 url_paths = {
     "{0}/v1/flows": response.dispatch,
     "{0}/v1/flows/(?P<flowarn>[^/.]+)": response.dispatch,
+    "{0}/v1/flows/(?P<flowarn>[^/.]+)/vpcInterfaces": response.dispatch,
+    "{0}/v1/flows/(?P<flowarn>[^/.]+)/outputs": response.dispatch,
     "{0}/v1/flows/start/(?P<flowarn>[^/.]+)": response.dispatch,
     "{0}/v1/flows/stop/(?P<flowarn>[^/.]+)": response.dispatch,
     "{0}/tags/(?P<resourcearn>[^/.]+)": response.dispatch,
diff --git a/tests/test_mediaconnect/test_mediaconnect.py b/tests/test_mediaconnect/test_mediaconnect.py
index 0e7d985da..07a5d8209 100644
--- a/tests/test_mediaconnect/test_mediaconnect.py
+++ b/tests/test_mediaconnect/test_mediaconnect.py
@@ -1,9 +1,12 @@
 from __future__ import unicode_literals
 
 import boto3
+import botocore
+import pytest
 import sure  # noqa
-from moto import mock_mediaconnect
+from botocore.exceptions import ClientError
 
+from moto import mock_mediaconnect
 
 region = "eu-west-1"
 
@@ -153,3 +156,93 @@ def test_tag_resource_succeeds():
     list_response = client.list_tags_for_resource(ResourceArn="some-arn")
     list_response["ResponseMetadata"]["HTTPStatusCode"].should.equal(200)
     list_response["Tags"].should.equal({"Tag1": "Value1"})
+
+
+@mock_mediaconnect
+def test_add_flow_vpc_interfaces_succeeds():
+    client = boto3.client("mediaconnect", region_name=region)
+    channel_config = _create_flow_config("test Flow 1")
+
+    create_response = client.create_flow(**channel_config)
+    create_response["ResponseMetadata"]["HTTPStatusCode"].should.equal(200)
+    create_response["Flow"]["Status"].should.equal("STANDBY")
+    flow_arn = create_response["Flow"]["FlowArn"]
+
+    client.add_flow_vpc_interfaces(
+        FlowArn=flow_arn,
+        VpcInterfaces=[
+            {
+                "Name": "VPCInterface",
+                "SubnetId": "",
+                "SecurityGroupIds": [],
+                "RoleArn": "",
+            }
+        ],
+    )
+
+    describe_response = client.describe_flow(FlowArn=flow_arn)
+    describe_response["ResponseMetadata"]["HTTPStatusCode"].should.equal(200)
+    describe_response["Flow"]["VpcInterfaces"].should.equal(
+        [
+            {
+                "Name": "VPCInterface",
+                "RoleArn": "",
+                "SecurityGroupIds": [],
+                "SubnetId": "",
+            }
+        ]
+    )
+
+
+@mock_mediaconnect
+def test_add_flow_vpc_interfaces_fails():
+    client = boto3.client("mediaconnect", region_name=region)
+    flow_arn = "unknown-flow"
+    with pytest.raises(ClientError) as err:
+        client.add_flow_vpc_interfaces(
+            FlowArn=flow_arn, VpcInterfaces=[],
+        )
+    err = err.value.response["Error"]
+    err["Code"].should.equal("NotFoundException")
+    err["Message"].should.equal(
+        "flow with arn=unknown-flow not found".format(str(flow_arn))
+    )
+
+
+@mock_mediaconnect
+def test_add_flow_outputs_succeeds():
+    client = boto3.client("mediaconnect", region_name=region)
+    channel_config = _create_flow_config("test Flow 1")
+
+    create_response = client.create_flow(**channel_config)
+    create_response["ResponseMetadata"]["HTTPStatusCode"].should.equal(200)
+    create_response["Flow"]["Status"].should.equal("STANDBY")
+    flow_arn = create_response["Flow"]["FlowArn"]
+
+    client.add_flow_outputs(
+        FlowArn=flow_arn,
+        Outputs=[
+            {"Description": "string", "Name": "string", "Port": 123, "Protocol": "rist"}
+        ],
+    )
+
+    describe_response = client.describe_flow(FlowArn=flow_arn)
+    describe_response["ResponseMetadata"]["HTTPStatusCode"].should.equal(200)
+    describe_response["Flow"]["Outputs"].should.equal(
+        [{"Description": "string", "Name": "string", "Port": 123}]
+    )
+
+
+@mock_mediaconnect
+def test_add_flow_outputs_fails():
+    client = boto3.client("mediaconnect", region_name=region)
+    flow_arn = "unknown-flow"
+    with pytest.raises(ClientError) as err:
+        client.add_flow_outputs(
+            FlowArn=flow_arn, Outputs=[],
+        )
+    err = err.value.response["Error"]
+    err["Code"].should.equal("NotFoundException")
+    err["Message"].should.equal(
+        "flow with arn=unknown-flow not found".format(str(flow_arn))
+    )