A side key assembly comprises a base plate, a first push button and a second push button. The base plate has an opening defined therein and two opposite sidewalls defined in the opening. The first push button is rotatably assembled to the base in the opening, and the first push button is situated adjacent to one of the sidewalls. The second push button is rotatably assembled to the first push button in the opening and the second push button is situated adjacent to another sidewall.