A method for identity mediation in an enterprise service bus is provided in the illustrative embodiments. A security information is received at the enterprise service bus from a first application executing in a first data processing system. The security information is a part of a request for service from a second application executing in a second data processing system. A part of the security information is identified to be transformed such that the part upon transformation is usable for handling the request by the second application. A security policy applicable to the identified part is selected and the identified part is transformed according to the security policy. The transforming results in a transformed security information. The transformed security information is sent to the second application.