An electrical connector assembly includes a male connector and a female connector for connectable to the male connector. The male connector includes a male insulating housing and a number of first terminals assembled on the male insulating housing. An anti-mistake insertion bulge extends from the top surface of the male insulating housing. The female connector includes a female insulating housing and a number of second terminals assembled to the female insulating housing for connecting with the first terminals. An anti-mistake insertion gap is defined in the top surface of the female insulating housing. Two cutouts are defined in two opposite sidewalls bounding the anti-mistake insertion gap to hold the anti-mistake insertion bulge.