Nanocomposites based on plasmonic nanoparticles and metal‐oxide semiconductors are emerging as promising materials for conversion of solar energy into chemical energy. In this work, a Au–ZnO nanocomposite film with notably enhanced photocatalytic activity is successfully prepared by a single‐step process. Both ZnO and Au nanoparticles are synthesized in situ during baking of the film spin‐coated from a solution of Zn(CH 3 COO) 2 and HAuCl 4 . Furthermore, it is shown that this precursor solution can be formulated as a nanoink for the generation of micropatterns by microplotter printing, opening the way for the miniaturization of devices with enhanced properties for photocatalysis, optoelectronics, and sensing. The study demonstrates that Au–ZnO films exhibit 4.5‐fold enhanced photocatalytic properties for the decomposition of methyl orange upon sunlight exposure in comparison with ZnO films. Au nanoparticles improve significantly the photocatalytic activity of ZnO because they act as photosensitizers, absorbing photons at the localized surface plasmon resonance range (500–600 nm) and transferring electrons to the nearby ZnO semiconductor. XPS analysis of the Au–ZnO nanocomposite supports this explanation, indicating strong interactions between Au and ZnO.