The development of technologies such as artificial intelligence and the Internet of Things has increased the demand for wearable, self-powered pressure sensors. Triboelectric nanogenerator (TENG)-based self-powered pressure sensors have emerged as a solution to meet this demand. However, the measurement of static and small pressure ranges remains a challenge. In this paper, we propose a self-powered pressure-sensing device based on the combination of carbon nanotube (CNT)/porous poly(dimethylsiloxane) (PDMS) composite and poly(ethylene oxide) (PEO) film. The proposed device could continuously and reliably measure static and small-range pressure through capacitive pressure sensing while harvesting energy based on the triboelectric effect. The device exhibited a remarkable sensitivity of 1.37 kPa–1 due to the incorporation of high-k materials (i.e., CNTs, a nanosized filler) in its porous structure and dielectric layer. It also had a power density of 15 mW/m2 due to the triboelectric interaction between PDMS and PEO. Finally, the fabricated device was connected to a microcontroller unit to perform energy harvesting and pressure sensing simultaneously, demonstrating its great potential as a wearable device.