A ferrite core integrated waterproof connector includes wires (WH) each having a terminal fittings (20) mounted thereon and a housing (10) with terminal accommodating chambers (12A, 12B) for accommodating the terminal fittings (20). A plate-like rubber plug (30) covers a rear surface (10B) of the housing (10) and has wire insertion holes (31) arranged to correspond to the terminal accommodating chambers (12A, 12B). Lips (32) are formed on the inner peripheral surfaces of the wire insertion holes (31) for closely contacting the outer peripheral surfaces of coatings of the wires (WH). At least one ferrite core (50) is embedded in the one-piece rubber plug (30) and has at least one hollow portion 52 concentric with at least some of the wire insertion holes (31). The ferrite core (50) is radially outward of base parts of the lips (32) of the one-piece rubber plug (30).