An approach for providing instant messaging (IM) services is disclosed. A request is received from a source client to establish communication with a destination client associated with a subscriber over a first IM environment, wherein the request specifies a first user name derived from a unique identifier of the subscriber. A unique identifier is determined from the first user name. Further, a profile of the subscriber is accessed based on the unique identifier to determine a second user name corresponding to a second IM environment. An IM session is established between the source client and the destination client over the first and second IM environments using the respective first user name and second user name.