The white‐rot fungus Stereum hirsutum was studied to evaluate its applicability for use in the biosynthesis of copper/copper oxide nanoparticles under different pH conditions and in the presence of three different copper salts (CuCl₂, CuSO₄, and Cu(NO₃)₂). The nanoparticle formation was evaluated by UV‐visible spectroscopy, electron microscopy (TEM), X‐ray diffraction analysis (XRD), and Fourier transforms infrared spectroscopy (FTIR). The nanoparticles biosynthesis in presence of all copper salts demonstrated higher formation with 5 mM CuCl₂ under alkaline conditions. TEM analysis confirmed that the nanoparticles were mainly spherical (5 to 20 nm). The presence of amine groups attached to nanoparticles was confirmed by FTIR, which suggests that extracellular protein of fungus is responsible for the formation of the nanoparticles. Therefore, the white‐rot fungus S. hirsutum was found to exhibit potential for use in the synthesis of copper/copper oxide nanoparticles.