An electrical connector comprises an insulating housing, several first and second conductive terminals, an inner grounding unit, and an outer grounding unit, which are disposed on the insulating housing. The insulating housing has a first surface, an opposite second surface, and two side surfaces arranged between the first and second surfaces. The inner grounding unit has a plate embedded in the insulating housing and two protruding sheets extended from the plate and respectively protruding from the side surfaces of the insulating housing. The plate is arranged to separate the first conductive terminals from the second conductive terminals. The outer grounding unit clips the insulating housing and engages the protruding sheets. A portion of the outer grounding unit engaged with one of the protruding sheets includes two stacked engaging portions, and at least one of the two stacked engaging portions has a thru-hole for engaging with the corresponding protruding sheet.