Sustainable and stable photodetectors with self-powering nature and superior performance are necessary to address the growing demand for flexible and wearable optoelectronic devices. This work demonstrates a flexible, self-powered, coaxial p-n heterojunction photodetector using SnS2/SnS on an Ag fiber substrate by coupling the photoexcitation property, semiconductor nature, and piezoelectric effect. Detailed characterization studies confirm the formation of hexagonal and orthorhombic crystal planes of SnS2 and SnS nanoflakes, respectively, with a piezoelectric coefficient (d33) of 175 pm/V for SnS2. The photoabsorption is maximum in the visible region with a direct band gap of 2.1 eV. The electrical studies display a tunable photoresponse under zero-bias conditions. Upon compressive strain of 0.43%, the photoresponse increases by 36%. The Ion/Ioff ratio of the fabricated photodetector was 102 at a zero bias, and the rise and decay times shorter than 1 s were obtained. The maximum external quantum efficiency of the fabricated photodetector was found to be 54.2%, owing to the superior piezo-phototronic properties. The band diagram and the charge transfer mechanism are studied to investigate the piezo-phototronic effect. The uniform strain on the Ag fiber substrate and the piezo-potential distribution upon compressive and tensile strain promotes carrier separation in the coaxial interfaces of the p-n junction. The demonstrated strategy provides a direction for developing fiber-based photodetectors with self-powering behavior and enhanced photoresponsivity for next-generation smart wearable textile-based applications. © 2023 American Chemical Society.