In this paper, a voltage controlled oscillator (VCO) with ultra low dc power consumption and low phase noise is proposed for 2.4 GHz Bluetooth. To reduce the dc power consumption, a novel bias circuit is proposed instead of a conventional tail-current circuit to decrease the supply voltage. In addition, the proposed VCO is designed to operate in sub-threshold region for decreasing the operation current. Thus, the dc power consumption is largely reduced. To improve the phase noise, a modified LC-tank is proposed to suppress the harmonic noise modulation and to prevent the phase noise degradation by the down-converted Flick noise. The LC-VCO is simulated using 0.11 μm CMOS technology. The simulation results show a phase noise of -115dBc/Hz at 1MHz offset from the 2.4 GHz carrier frequency with only 0.35 mW power consumption.