This letter reports a 4x W-band quasi-subharmonic down-conversion mixer in a 65 nm CMOS technology. Developed from subharmonic mixers, this mixer saves trouble in designing phase-shifters and works well within W-band. Down-conversion is achieved by capturing the phase difference between two sine waves at every half cycle of the local oscillator. The power gain is above 3.5 dB over the entire W-band. The minimum noise figure is 12.5 dB, and the 1 dB compression point is -1.2 dBm.