This brief presents a 0.9-μW duty-cycle-modulated temperature sensor with a sub-μA peak current for energy harvester- or micro-battery-powered systems. A compact sensing frontend is proposed to achieve low power, together with various device-level leakage and nonlinearity compensation techniques adopted to minimize the sensor error. In addition, a current-starved multivibrator which provides inherent clamping voltages is used for duty cycle modulation for overall energy savings. The sensor designed in 0.18-μm CMOS process achieves a resolution figure of merit of 10.6 pJ.K, which is among the most energy-efficient designs to date. Trimmed at 30 °C, the sensor achieves ±0.85 °C precision from -30 °C to 120 °C. The maximum supply sensitivity is 0.7 °C/V for a 1.6-2 V supply.