Delafossite AgFeO₂ nanoparticles were synthesized by the modified hydrothermal procedure for excellent photochemical performances for the removal of organic dye from neutral and alkaline aqueous medium. The structure, morphology, and elemental studies of the delafossite AgFeO₂ nanoparticles were done by analytical methods. AgFeO₂ nanoparticles show the refined lattice parameters of “a” = 3.033(2) Å and “c” = 18.591(3) Å of R3m phase. The excellent photocatalytic performance of delafossite AgFeO₂ nanoparticles was observed under the full sunlight irradiations, which resulted ~92% degradation of methylene blue (MB) dye in 40 min using alkaline medium. The kinetic studies confirm the pseudo-first-order reactions of MB dye degradation in presence of photocatalysts. The fragmentations of organic dye molecules in presence of delafossite AgFeO₂ photocatalysts under sunlight irradiations were also studied using the GC–MS technique. The delafossite AgFeO₂ nanoparticles show excellent photocatalytic regeneration efficiency.