A board-to-board connector assembly includes a receptacle connector having a plurality of first terminals, and a plug connector having a plurality of second terminals. Each of the first terminals has a first contact portion and a second contact portion and each of the second terminals has a first contact arm and a second contact arm. When the plug connector is mated with the receptacle connector, the first contact portion and the second contact portion of the first terminal electrically contact the first contact arm and the second contact arm of the corresponding second terminal respectively to make the first terminal and the corresponding second terminal electrically interconnected steadily.