In this study, we demonstrate the first successful application of InP quantum dots (QDs) as an environmentally friendly visible light photocatalyst for water treatment. The QDs were synthesized using a hot injection method followed by a surface ligand exchange with sulphide ions (S2−) to render them water-dispersible. The photocatalytic activity of the QDs was assessed by examining their ability to degrade two common water contaminants: caffeic acid (CA) and 4-hydroxyphenylacetic acid (4-HPA) under visible light irradiation. After 4 hours of irradiation, 60% of CA was removed as compared to 30% of 4-HPA. In contrast, no significant degradation was observed using TiO2. The decomposition kinetics of CA was further studied and was found to follow a first order kinetic model.