A card edge connector for mating with an electronic card includes an elongated housing, a number of contacts and a retainer retained to the housing. The housing has a pair of side walls, a central slot between the side walls and a first tower upwardly extending at one end thereof. The first tower defines a first U-shaped cavity downwardly extending from a top end thereof and a mounting slot upwardly extending from a lower end thereof and located at outside of the first cavity. The first cavity communicates with the central slot along a length direction of the housing to receive the electronic card. The retainer has a non-flexible fastening portion retained in the mounting slot and a flexible locking barb obliquely protruding into the first cavity from a top end of the fastening portion to lock with the electronic card.