A method for calibrating a vehicular sensing system includes disposing the sensing system at a vehicle, with the sensing system including at least two radar sensors disposed at the vehicle so as to have respective fields of sensing exterior of the vehicle. At least one spherical radar reflector is disposed at a position exterior the vehicle where the fields of sensing of the at least two radar sensors overlap. A calibration mode of the sensing system is entered, and calibration radio waves are transmitted by at least one transmitter, and reflected calibration radio waves are received by receivers of the at least two radar sensors. The reflected calibration radio waves include the calibration radio waves reflected off the at least one spherical radar reflector. A controller calibrates the sensing system responsive to processing the received reflected calibration radio waves.