In this study, Fe2O3/graphitic carbon nitride (g‐CN) composites were fabricated using a simple calcination method. Iron chloride and urea were used as starting precursors for preparation of heterojunction composites (Fe2O3/g‐CN) by a quick stirring and calcination method. A sequence of Fe2O3/g‐CN composites were obtained by putting a specific amount of Fe2O3 on the surface of g‐CN at varied temperature (400, 450 and 500 °C). We accomplished a combined analysis using x‐ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR), electron paramagnetic resonance (EPR), elemental analysis spectra (EAS), Brunauer–Emmett–Teller analysis (BET), diffuse reflectance spectra (DRS) and photoluminescence spectra (Pl) of resulting samples. Our findings demonstrate that Fe/CNx composites demonstrating a significant improvement in the separation of photogenerated carriers and hole formation, leading towards momentous photocatalytic activity. For the first time, the as‐synthesized composites were used for hydrogen production (water reduction) and methylene blue photodegradation under visible light illumination (λ = 420 nm). The superior sample Fe/CN450 exhibits an exceptional photocatalytic efficiency in both electron generation (hydrogen evolution rate) and hole formation (photodegradation) with a rate of 91.1% at 180 min. Along with this, Fe/CN450 has excellent photochemical stability in hydrogen evolution and pollutant removal. The potential photocatalytic mechanism of Fe/CN450 composite is compared with experimental results to characterize the photocatalytic phenomenon as a whole. © 2021 Society of Chemical Industry