An electronic device may be provided with wireless circuitry and a housing with upper and lower ends. The upper end may include first and second inverted-F antennas formed from portions of conductive peripheral housing structures separated from an antenna ground by a slot. The upper end may include an open slot antenna formed from a portion of the slot. The upper end may include an additional inverted-F antenna that overlap the slot. A parasitic element may be disposed between the open slot antenna and the additional inverted-F antenna and coupled to the antenna ground at a proximal end. A tuning component may be coupled between the parasitic element and the antenna ground.