A vehicular radar sensing system includes a radar sensor disposed at a vehicle so as to sense exterior of the vehicle and having at least one transmitter that transmits radio signals and at least one receiver that receives radio signals. The radar sensor includes a transmitting wave guide antenna and a receiving wave guide antenna, a PCB, and a processor operable to process radio signals transmitted by the at least one transmitter and received by the at least one receiver. Each of the wave guide elements includes a respective wave guide slot disposed at the inboard side of the PCB, and another respective wave guide slot that guides the radio signals to or from the environment, and a respective air wave guide that guides the radio signals between the respective wave guide slots.