New titania-reduced graphene oxide (TiO2-rGO) nanocomposites have been studied to assess their application in the solar assisted photodegradation of a complex mixing of pesticides (pyrimethanil, isoproturon, alachlor and methomyl) at solar pilot plant, opening the opportunity to extend the use of these hybrid photocatalysts to complex wastewater effluents. TiO2-rGO nanocomposites were prepared by hydrothermal method from two commercial TiO2, Hombikat UV-100 (HBK) and Aeroxide (R) P25 (P25). The effect of two different water matrices (simulated and natural) on TiO2-rGO solar photoefficiency with two pesticides concentrations (5 mg center dot L-1 and 200 mu g center dot L-1), and the additional use of an electron scavenging as oxidant agent, such as hydrogen peroxide in a comparison with oxygen from air, has been studied in compound parabolic collectors (CPC) photoreactors. Best photocatalytic performances were always found with oxygen over both TiO2-rGO nanocomposites, regardless of the water matrix employed. The use of H2O2 as oxidant agent has not improved the final photocatalytic efficiency in any case. The generation of secondary highly reactive species in the reaction media from reaction of SO4?- /HO center dot radicals, and the more negatively surface charge with low SBET of P25-rGO nanocomposite, besides its lower hydrodynamic size with lower particle aggregation in the reaction conditions, have been responsible to promote the photo-oxidation of the complex pesticides mix studied. Finally, HBK TiO2-reduced graphene oxide (HBKrGO) nanocomposite has presented excellent solar photoefficiency in the photodegradation of 200 mu g center dot L-1 of each pesticide with the oxygen form air, especially under natural water matrix, because of its large negatively charge surface area where probably recombination of electrons and holes is prevented.