An electrical connector assembly comprises: an insulative housing defining a receiving space therein communicated with an exterior along a longitudinal direction. The insulative housing defines a resilient latch mechanism integrally formed on a top surface thereof and a pair of projecting portions located at two opposite sides of the latch mechanism for preventing a rotational movement with respect to a complementary mating connector. Two printed circuit board (PCB) modules are arranged in substantially a stacked manner and received into the receiving space. And, a retainer fixes the two PCB modules to the insulative housing.