Abstract The effect of the simultaneous presence of fluoride (0.15–1.2 mg L −1 ), bicarbonates (83.6–596 mg L −1 ), and synthesized goethite (0.3 mg L −1 ) at typical concentrations often found in groundwater samples was evaluated on the degradation of 2,4‐dichlorophenoxyacetic acid (2,4‐D) at pH 6.9 under simulated sunlight irradiation (300 W m −2 ) and H 2 O 2 concentrations of 10 mg L −1 . The 2,4‐D removal was strongly enhanced by the presence of fluoride. F − could modify the surface of iron (hydr)oxide, leading to the formation of surface Fe–F bonds benefiting the formation of free • OH, producing upward band bending, reducing the electron‐hole recombination, and enhancing the electron transfer to H 2 O 2 . On the other hand, bicarbonate may react with • OH generating CO 3 −• species that could participate in pollutant oxidation, while solar light‐induced H 2 O 2 photolysis also played an important role in removing 2,4‐D. These findings suggest that tuning of iron (hydr)oxides by fluoride could take place in real groundwater, generating photocatalysts with a high activity that could participate, by adding H 2 O 2 , in the enhancement of sunlight photoinduced natural abiotic processes for pollutant abatement.