An electrical connector includes a contact module enclosed within a metallic main shell. The contact module includes an insulative housing and a plurality of contacts retained in the housing. The housing includes a base and a tongue portion extending forwardly from the base. The main shell is formed by stamping and forming, and includes opposite first and second side walls, and a pair of end walls linking the opposite first and second side walls. The shell forms a mating cavity enclosing the tongue portion. A seam is formed on the second side wall. An adhesive layer is applied upon an exterior surface of the second side wall to cover the seam for providing a waterproof function. A metallic sub-shell is attached upon the adhesive layer.