•BaTiO3@g-C3N4 composites were prepared by a simple mixing–calcining method.•The composites exhibit enhanced photocatalytic activity compared to bare BaTiO3 and g-C3N4.•The effect of BQ, AO and ethanol on the photocatalytic efficiency was investigated.•O2 and h+ are the main active species responsible for the dye degradation.•OH radicals play a relatively small role in the photocatalytic reaction. BaTiO3@g-C3N4 composites were prepared by a simple mixing–calcining method. SEM observation indicates that BaTiO3 nanoparticles are uniformly assembled onto the surface of g-C3N4 platelets. The photocatalytic activity of as-prepared BaTiO3@g-C3N4 composites were evaluated by the degradation of methyl orange (MO) under simulated sunlight irradiation, revealing that the composites exhibit enhanced photocatalytic activity compared to bare BaTiO3 and g-C3N4. This can be explained by the efficient separation of the photogenerated electron–hole pairs due to the migration of the carriers between g-C3N4 and BaTiO3; as a result, electrons and holes are increasingly available for the photocatalytic reaction. Hydroxyl radicals were detected by the photoluminescence technique using terephthalic acid as a probe molecule and are found to be produced equally on the irradiated BaTiO3 particles and BaTiO3@g-C3N4 composites. The effect of benzoquinone, ammonium oxalate and ethanol on the photocatalytic efficiency was also investigated. According to the experimental results, superoxide radicals and photogenerated holes are suggested to be the main active species responsible for the dye degradation, while hydroxyl radicals play a relatively small role in the photocatalytic reaction.