The increasing global demand for renewable and sustainable energy sources has driven intensive research into the development of efficient photovoltaic materials and the exploitation of solar energy for green hydrogen production. However, the synthesis of low-cost, environmentally benign, and high-performance materials remains a persistent challenge. In this study, CuO thin films were fabricated using the molecular precursor method (MPM) and deposited onto quartz substrates via spin coating, followed by heat treatment at 600 °C. The structural, optical, photocatalytic, and photocurrent properties of the thin films were investigated. XRD analyses revealed high crystallinity with average grain sizes of ~70 nm for CuO. Moreover, the UV–Vis spectroscopy confirmed CuO bandgap of 2.2 eV, consistent with previously reported MPM-derived films. Photocatalytic degradation of methylene blue (MB) under 1 Sun illumination showed unexpectedly high photolysis in the blank solution (>95% removal in 3 h), overshadowing the intrinsic catalytic activities of the films. SEM images showed rough, high-surface-area morphologies favorable for adsorption, but film thickness and MB solution depth likely limited effective photon–film interaction. The results indicate that further optimization; including reduction of solution depth, adjustment of film viscosity and thickness, and evaluation under controlled light intensities, is necessary for accurately assessing photocatalytic performance. This study provides foundational data for improving the photocataltic and photocurrent propperties of MPM-derived copper oxide films.