Using sustainable photocatalysts, photocatalytic degradation has emerged as one of the viable strategies to combat water pollution through eco-friendly and cost-effective means. Visible-light-active Ag3PO4/Mn-ZnO nanocomposite photocatalysts were produced in this study using a simple hydrothermal method and varied concentrations of Ag3PO4 to Mn-ZnO ranging from 0 to 5 wt percent. X-ray diffraction, scanning electron microcopy, energy-dispersive X-ray, transmission electron microscopy, UV–visible spectroscopy, Fourier transform infra-red spectrophotometer, and photoluminescence spectroscopy were used to examine the structural, morphological, and optical properties of synthesized materials. Visible light was used to test the photocatalytic activity of produced Ag3PO4/Mn-ZnO photocatalysts for the breakdown of tetracycline (TC) hydrochloride. In comparison to the other samples, the 3% Ag3PO4/Mn-ZnO nanocomposite exhibited superior activity as a result of improved visible light absorption and suppressed charge carrier recombination. In addition, this sample demonstrated good stability of TC in an aqueous environment after five consecutive cycles. This research will enhance the scope of photocatalysis for environmental applications.