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 fitting section upwardly extending at one end thereof. The fitting section 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 is retained in the mounting slot and has a locking projection protruding into the first cavity to lock with the electronic card. The mounting slot does not extend through the fitting section to make the retainer hidden in the fitting section.