A dual band 0.18µm 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 1.1V, 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 3.7mW (6.2mW) at low (high) band. The total area including the output buffer and the pads is 0.841 × 0.764mm².