Disclosed are various approaches for workflow service back end integration. In some examples, a hosting location is identified for a connector that handles communications with a network service. Authentication information that is selected based on the hosting location of the connector is appended to a service request. The authentication information includes a service credential that the connector uses to authenticate with the network service, if the connector is hosted locally to the workflow service. The authentication information includes instructions for the connector to retrieve the service credential from an enterprise-hosted data store, if the connector is hosted external to the workflow service. The service request is then transmitted with the selected authentication information.