This paper reports on a novel three-axis thermal accelerometer based on a buckled cantilever, out-of-plane microstructure. The thermal accelerometer has been fabricated using a polyimide-based surface micromachining technology. Our design incorporates multiple thermocouples, hence achieving high sensitivity with half the power consumption compared to our previous work. The X-, Y-, Z-axes sensitivity of the device is 10 μV/g, 14.4 μV/g, 9.8 μV/g respectively with a 2.5 mW total heater power. Experimental results show the device has a linear response and low cross-axis sensitivity. This paper describes the design, fabrication, assembly, and functional results of the thermal accelerometer.