Different copper based-materials have been used for controlling some fungal and bacterial pathogens. However, the antifungal activity of the copper-based materials depends on different parameters, such as the crystal phase, synthesis route, and size of the particles. Herein a facile route synthesis method of Cu/CuxO-NPs was achieved through the aqueous phase. The influence of NaBH4 concentration on the phase composition was studied. The synthesized Cu/CuxO-NPs were characterized by X-Ray diffraction (XRD), Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering. Five Cu/CuxO-NPs with different phase composition and nanoparticle size were obtained. The antifungal activity of the synthesized Cu/CuxO-NPs was studied in vitro against Fusarium oxysporum. The results indicate that a high percent of inhibition of radial growth (IGR) was obtained with NPs, which have a higher proportion of Cu2O phase and relatively smaller size particles. Furthermore, hypha morphology, membrane damage and production of reactive oxygen species (ROS) was evaluated with SEM and confocal microscopy.