An injection-current-boosting (ICB) locking-range enhancement technique is presented to increase the locking range (LR) of the millimeter-wave (mm-wave) injection-locked frequency triplers (ILFTs). With a transformer-based fourth-order injection-coupling network, the parallel capacitance from the injection devices is resonated out over a wide frequency range and the injection current is boosted greatly. Analytical models of the ICB–ILFT are introduced, based on which the current-boosting phenomenon is analyzed. Meanwhile, the design concepts of the ultra-wideband mm-wave ILFT are presented. With the proposed ICB technique, an ICB-ILFT is designed and fabricated in 65-nm CMOS process. With a 0-dBm RF injection source, the ICB-ILFT can be locked from 22.8 to 43.2 GHz without calibration, achieving a 61.8% LR. The power consumption is only 5.0 mW and a 9.5-dB phase noise difference is observed, which is close to the theoretical value.