A dual band 0.18 µm CMOS LC-tank injection locked frequency divider (ILFD) is proposed. The ILFD circuit is realized with a cross-coupled pMOS LC-tank oscillator with an inductor switch for frequency band selection. The self-oscillating VCO is injection-locked by nth-harmonic input to obtain the division factor of n. The division ratio of 1, 2, and 3 has been found for the proposed ILFD. Measurement results show that at the supply voltage of 1.1 V, the free-running frequency is from 2.28(3.09) GHz to 2.78(3.72) GHz for the low- (high-) frequency band. The power consumption of the ILFD core is 3.7 mW (6.2 mW) at low (high) band. The total area including the output buffer and the pads is 0.8410.764 mm2.