diff --git a/moto/ec2/models.py b/moto/ec2/models.py
index ff766d7b8..ef1425ea7 100644
--- a/moto/ec2/models.py
+++ b/moto/ec2/models.py
@@ -189,7 +189,7 @@ class NetworkInterface(TaggedEC2Resource):
         self.ec2_backend = ec2_backend
         self.id = random_eni_id()
         self.device_index = device_index
-        self.private_ip_address = private_ip_address
+        self.private_ip_address = private_ip_address or random_private_ip()
         self.subnet = subnet
         self.instance = None
         self.attachment_id = None
diff --git a/tests/test_cloudformation/fixtures/vpc_eni.py b/tests/test_cloudformation/fixtures/vpc_eni.py
index ef9eb1d08..3f8eb2d03 100644
--- a/tests/test_cloudformation/fixtures/vpc_eni.py
+++ b/tests/test_cloudformation/fixtures/vpc_eni.py
@@ -29,6 +29,10 @@ template = {
         "NinjaENI": {
             "Description": "Elastic IP mapping to Auto-Scaling Group",
             "Value": {"Ref": "ENI"}
+        },
+        "ENIIpAddress": {
+            "Description": "ENI's Private IP address",
+            "Value": {"Fn::GetAtt": ["ENI", "PrimaryPrivateIpAddress"]}
         }
     }
 }
diff --git a/tests/test_ec2/test_elastic_network_interfaces.py b/tests/test_ec2/test_elastic_network_interfaces.py
index 828f9d917..70e78ae12 100644
--- a/tests/test_ec2/test_elastic_network_interfaces.py
+++ b/tests/test_ec2/test_elastic_network_interfaces.py
@@ -36,7 +36,8 @@ def test_elastic_network_interfaces():
     all_enis.should.have.length_of(1)
     eni = all_enis[0]
     eni.groups.should.have.length_of(0)
-    eni.private_ip_addresses.should.have.length_of(0)
+    eni.private_ip_addresses.should.have.length_of(1)
+    eni.private_ip_addresses[0].private_ip_address.startswith('10.').should.be.true
 
     with assert_raises(EC2ResponseError) as ex:
         conn.delete_network_interface(eni.id, dry_run=True)
@@ -354,9 +355,13 @@ def test_elastic_network_interfaces_cloudformation():
     )
     ec2_conn = boto.ec2.connect_to_region("us-west-1")
     eni = ec2_conn.get_all_network_interfaces()[0]
+    eni.private_ip_addresses.should.have.length_of(1)
 
     stack = conn.describe_stacks()[0]
     resources = stack.describe_resources()
     cfn_eni = [resource for resource in resources if resource.resource_type ==
                'AWS::EC2::NetworkInterface'][0]
     cfn_eni.physical_resource_id.should.equal(eni.id)
+
+    outputs = {output.key: output.value for output in stack.outputs}
+    outputs['ENIIpAddress'].should.equal(eni.private_ip_addresses[0].private_ip_address)