An electrical connector assembly comprises: a metallic housing having a receiving space extending along a longitudinal and two openings respectively formed on top and bottom surfaces thereof and communicated with the receiving space; a pair of flexible printed circuit boards (FPCs) received into the receiving space and arranged in a back-to-back manner. Each of the FPC defines a protuberant portion extending into the corresponding opening. And each of the protuberant portion has a plurality of contacts formed on one side thereof and communicated with an exterior. A pair of supporting pieces are received into the receiving space and attached to another side of the protuberant portion. And a spacer is received into the receiving space and sandwiched between the pair of flexible printed circuit boards and supporting pieces.