An electrical connector assembly includes a connector housing defining a plurality of terminal cavities in which electrical terminals attached to wire cables are received, a mat seal formed of a compliant material and having a plurality of seal apertures through which the electrical terminals are inserted into the plurality of terminal cavities, and a seal retainer. The mat seal is disposed between the seal retainer and the connector housing and wherein the seal retainer is connected to the connector housing by a flexible member configured to urge the mat seal into contact with the connector housing and allow longitudinal movement of the seal retainer relative to the connector housing. A method of assembling such an electrical connector is also provided.