An electronic device has wireless communications circuitry including a triplexer. The wireless communications circuitry may be used in first and second modes. In the first mode, the device communicates in a first communications band using a transmitter in a first uplink frequency range associated with the first communications band and using a receiver in a first downlink frequency range associated with the first communications band. In the second mode, the device communicates in a second communications band using a transmitter to transmit in a second uplink frequency range associated with the second communications band and using the receiver to receive in a second downlink frequency range associated with the second communications band. Signals in the two downlink frequency ranges may pass through a common bandpass filter in the triplexer. Two additional bandpass filters in the triplexer may be used to respectively handle the two uplink frequency ranges.