This letter presents the design and implementation of a wideband 24 GHz amplitude monopulse comparator in 0.13 mu m CMOS technology. The circuit results in 9.6 dB gain in the sum channel at 24 GHz with a 3-dB bandwidth of 234-25.2 GHz, and a sum/difference ratio of > 25 dB at 20-26 GHz. The measured input P1 dB is -14.4 dBm at 24 GHz. The chip is only 0.55 x 0.50 mm(2) (without pads) and consumes 44 mA from a 1.5 V supply, including the input active baluns and the differential to single-ended output stages (28 mA without the input and output stages). To our knowledge, this is the first demonstration of a high performance mm-wave CMOS monopulse comparator RFIC.