A frequency-tracking technique is proposed to enhance the locking range of millimeter-wave (mmW) injection-locked frequency dividers (ILFDs). An improved model is introduced for direct-injection ILFDs, based on which both the phase and gain conditions are analyzed and discussed. Moreover, a method of admittance locus is applied to obtain the design intuition for optimization and to predict the locking range accurately. Finally, with the proposed model and design methodology, a frequency-tracking ILFD is designed and fabricated in a 65-nm CMOS process, which measures a locking range of 39.2% from 53.4 to 79.4 GHz while consuming 2.9 mW from an 0.8-V power supply, which corresponds to an FoM of 8.97 GHz/mW.