The enormous demand for self-powered sensors in industry 4.0 has drawn a lot of research interest in these vital devices that do not need external power sources. This study presents the development of a self-powered paper-based humidity sensor that uses copper and aluminium as electrodes and a composite of MgCl2 and carbon nanotubes (CNTs) as sensing material. The results demonstrate a significant improvement in humidity sensing performance as a result of the addition of CNTs and MgCl2. In particular, the self-powered paper-based humidity sensor with MgCl2/CNTs composites has impressive repeatability, broad detection ranging from 11 % to 97 % relative humidity, and quick response and recovery times of 10 and 46 s, respectively. Furthermore, the self-powered paper-based humidity sensor can generate a maximum voltage of 1.07 V and a maximum power of approximately 1.984 µW. Furthermore, connecting the paper-based humidity sensors in series increases their voltage output, making them useful for charging capacitors and lighting up to six LEDs. This endeavour offers a straightforward, cost-effective, and highly responsive self-powered paper-based humidity sensor that is ideal for high-performance applications in humidity sensing within power generation fields.