AbstractHerein, S‐doped graphene flakes‐based composites with Fe3O4 and/or CuS nanoparticles (NPs) are reported as photo‐Fenton catalysts for the 4‐nitrophenol (4‐NP) degradation. The S‐doped graphene flakes (S‐GF) were prepared using a thermal treatment approach, and the nanocomposites by the in situ growth of Fe3O4 and/or CuS onto the S‐GF scaffold. The characterization methods confirmed the formation of two‐ and three‐components nanocomposites. The Fe3O4 NPs presented a cubic inverse spinel structure and the CuS phases a covellite structure, both with smaller crystallite sizes in the nanocomposites. The new nanocomposites showed higher ability to catalyze the photo‐Fenton 4‐NP degradation than the individual components. The S‐GF@CuS−Fe3O4 nanocomposite exhibited the best catalytic activity: 95.2 % of 4‐NP degradation, a kinetic of pseudo‐first order (k=0.016 min−1), high photo‐Fenton catalytic stability and catalyst's composition/structure preservation. The CuS NPs showed an important role in the photo‐Fenton‐like catalytic activity improvement.