A door frame assembly and method of mounting the same, which does not require the use of exterior fasteners to secure members of the door frame assembly to a support frame in a doorway of a building. A connecting member is securable to a support frame member. A doorjamb member is attachable to the connecting member. A trim member is attachable to the connecting member and the door jamb member. The connecting combinations between the connecting member, the door jamb member and the trim member are such that once the door frame assembly is fully assembled, the door jamb member and the trim member cannot be disconnected from the support frame member absent an intervening force.