Metal oxide nanoparticles of different nature have been used in different fields such as therapeutics, biomarkers, tribology or environmental remediation, among others. Besides, the surface modification of such nanoparticles is of particular interest to bring designed functions. In this paper we describe the synthesis of CuO nanoparticles with two different geometries (spherical and prolate) and decorated with long alkyl chains in order to use as dye removers by adsorption and/or photo-degradation of a persistent model dye (Congo Red) and as lubricant additives to improve the tribological performance of base lubricant oils. Alkyl-functionalized CuO nanoparticles demonstrated a high stability in oily suspensions and an improvement in the friction reducing the CoF ca. 26%; the alkyl-decorated nanoparticles showed also higher adsorption kinetics for Congo Red than the neat ones following a pseudo-second-order trend, although with lower adsorption efficiency. The synthesis, surface modification and physic-chemical characterization of spherical and prolate CuO nanoparticles are described as well as their applications as lubricant additives and Congo Red photocatalytic removal.