An electrical connector includes an insulative housing, a plurality of contacts retained in the insulative housing, a fastener and a first sealing ring. The insulative housing has a rear section extending backwardly. The rear section has a rear space and a first peripheral wall around the rear space. Each contact has a connecting leg extending into the rear space. The fastener has a mating section to engage with the rear section and a board receiving chamber extending therethrough along a front to back direction. The fastener has a fixed position on the insulative housing, and as moving the fastener to the fixed position, the connecting legs are pressed into the board receiving chamber for electrically connecting with the flexible printed circuit board, and the first sealing ring is sealed around the junction of the contacts and the flexible printed circuit board.