A board-to-board connector assembly includes a receptacle connector and a plug connector mated with each other. The receptacle connector includes a first body, first terminals and a pair of first metal members. The first body includes an island structure and a first receiving slot surrounding the island structure. The first terminals are respectively disposed on a first side and a second side of the first receiving slot, the first and second sides being opposite to each other. The first metal members are respectively disposed on a third side and a fourth side of the first receiving slot, the third and fourth sides being opposite to each other. The first metal member includes a base extending to a bottom on the third side or a bottom on the fourth side, and a pair of first elastic arms extending from the base and facing away from each other.