A vehicular radar sensing system includes a radar sensor configured to be disposed at a vehicle. The radar sensor includes a plurality of antennas that include a plurality of transmitting antennas that transmit radio signals and a plurality of receiving antennas that receive radio signals. The radar sensor provides radar data to a processor that processes the provided radar data to detect an object present in the field of sensing of the radar sensor. At least some antennas of the plurality of antennas include waveguides having T-shaped slots, with each T-shaped slot having a longitudinal portion and a transverse portion that extends transverse from the longitudinal portion, and with a width of the transverse portion being less than a length of the longitudinal portion.