Fe coordination is effective to promote photocatalytic Cr(VI) reduction by graphitic carbon nitride (g-C3N4) from wastewater; however, the role of Fe coordination in the Cr intermediate transformation is still unknown. Herein, a Cr intermediate, Cr(V), is detected by electron paramagnetic resonance and its generation and consumption kinetics are constructed for studying the visible-light photocatalytic processes of g-C3N4 and Fe anchored g-C3N4. The inclusion of Fe increased the photocatalytic Cr(VI) removal from 26.8 % to 51.3–85.6 %. The results reveal that Fe coordination of trivalent state can greatly enhance photocatalytic Cr(VI) reduction performance mainly through promoting interfacial electron transfer from g-C3N4 to Cr(V). Compared with pure g-C3N4, increasing Fe(III)/Fe(II) ratio of coordinated Fe species results in 8–11 times of enhancement of photocatalytic Cr(VI) reduction performance, 1–2 times of enhancement of photocatalytic Cr(V) generation, and 8–9 times of enhancement of photocatalytic Cr(V) consumption. This suggests the rate-limiting step for Cr(VI) reduction by g-C3N4-based photocatalysts is the transformation process of Cr(V) to Cr(III) and also illustrates the important role of the coordinated Fe(III) species in the photocatalytic transformation of Cr intermediates. This study deepens the understanding of Fe-coordination-promoted photocatalytic Cr(VI) reduction process and sheds light on developing high-performance g-C3N4-based photocatalysts for Cr(VI) removal from wastewater.