It is well established that introducing nanoparticles into the solder metallic enhances its properties. This study aims to investigate the influence of adding a small amount of CuO nanoparticles on the microstructure, thermal properties, and electrical conductivity of environmentally friendly eutectic Sn90-x-Zn10-CuOx solder alloys. The solder alloys are prepared with varying CuO nanoparticle concentrations, specifically x = 0, 0.05, 0.1, 0.3, 0.5, and 1 wt. %. The study focuses on the evaluation of structure, thermal, and electrical properties, as well as the microstructure conditions of materials containing nanoparticles. To accomplish this, various techniques such as X-ray diffraction, and scanning electron microscopy were employed. X-ray diffraction and scanning electron microscopy were utilized to identify the phases present and examine the morphology features. Here we show that the microstructure investigations indicated that the incorporation of CuO nanoparticles into eutectic Sn-10Zn resulted in a reduction in crystallite size and led to finer and more homogeneous microstructure. Additionally, the addition of CuO nanoparticles led to an increase in the melting temperature and increased the electrical resistivity compared to the plain solder.