A rear and side object detection system for a vehicle based on monolithic millimeter wave integrated circuit technology. A multiple antenna configuration is employed that defines six sensing regions to the right, left and the rear of the vehicle. A sixth sensing region is defined at the right side of the vehicle, a second sensing region is defined at the right side and rear of the vehicle and overlaps the sixth sensing region, a fourth sensing region and a first sensing region extend from the rear on both sides of the vehicle in the adjacent lanes, a third sensing region is defined at the left side of the vehicle and a fifth sensing region is defined at the left side and rear of the vehicle and overlaps the second and third sensing regions. A right side warning signal is issued if an object is detected in a right side detection zone defined by the sixth sensing region or a portion of the second sensing region that does not overlap the fourth or fifth sensing regions. Likewise, a left side warning signal is issued if an object is detected in a left side detection zone defined by the third region and a portion of the fifth sensing region that does not overlap the second or first sensing regions. A back-up warning signal is issued if an object is detected in an overlap region between the second and fifth sensing regions.