Pure AgX (X = Cl, Br, I) nanomaterials have been synthesized through a simple solvothermal method. Their visible-light-responsive photocatalytic activities have been estimated from the degradation of the organic dye rhodamine B (RhB) and the colorless antibiotic oxytetracycline (OTC). Importantly, the effect of light irradiation on the photostability of AgX (X = Cl, Br, I) during photocatalysis, which has not been previously reported, has been investigated herein.