In the present study, a nanocomposite material g-C3N4/Fe-TiO2 has been prepared successfully by a simple one-step hydrothermal process and its structural properties were thoroughly studied by various characterization techniques, such as X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, electron paramagnetic resonance (EPR) spectrum, X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectrometry (UV-vis DRS). The performance of the fabricated composite material towards the removal of phenol from aqueous phase was systematically evaluated by a photocatalytic approach and found to be highly dependent on the content of Fe3+. The optimum concentration of Fe3+ doping that showed a dramatic enhancement in the photocatalytic activity of the composite under visible light irradiation was observed to be 0.05% by weight. The separation mechanism of photogenerated electrons and holes of the g-C3N4/Fe-TiO2 photocatalysts was established by a photoluminescence technique in which the reactive species generated during the photocatalytic treatment process was quantified. The enhanced photocatalytic performance observed for g-C3N4-Fe/TiO2 was ascribed to a cumulative impact of both g-C3N4 and Fe that extended its spectrum-absorptive nature into the visible region. The heterojunction formation in the fabricated photocatalysts not only facilitated the separation of the photogenerated charge carriers but also retained its strong oxidation and reduction ability.