A plug connector assembly (1) adapted to plug into a receptacle in two reversed directions, includes a mating member (10), a cable (30) electrically connected with the mating member, and an outer shell (50) including a main body (51), and a strain relief member (52) disposed at a rear end of the main body and enclosing the cable. The main body includes a front portion (510) enclosing a rear end (102) of the mating member, and a rear portion (511) opposite to the front portion and connected with the strain relief member. A thickness of the front portion is smaller than a thickness of the rear portion measured along a vertical direction. A thickness of the outer shell measured along the vertical direction is gradually increased in a constant slope along a front to rear direction