The effect of plasmonic nanoparticles (NPs) on the photoelectrochemical water splitting performance of CuWO 4 is studied here for the first time. CuWO 4 thin films were functionalized with well-defined Au NPs in two composite configurations: with the NPs (I) at the CuWO 4 −electrolyte interface and (II) at the CuWO 4 back contact. In both cases, the incident photon to current conversion efficiency of the film was increased (∼6-fold and ∼1.2-fold for configurations I and II (at λ = 390 nm), respectively). Two important advantages of placing the NPs on the CuWO 4 −electrolyte interface are identified: (1) Au NPs, coated with a 2 nm TiO 2 layer, are found to significantly enhance the surface catalysis of the film, decreasing the surface charge recombination from ∼60% to ∼10%, and (2) the NP's near-field can promote additional charge carriers within the space charge layer region, where they undergo field-assisted transport, essentially avoiding recombination. Our study shows that Au NPs, coated with a 2 nm TiO 2 layer, can significantly mitigate the catalytic and optical photoelectrochemical (PEC) limitations of CuWO 4. An increase from 0.03 to 0.1 mA cm −2 in the water-splitting photocurrent was measured for a 200 nm film under simulated solar irradiation at 1.23 V vs RHE.