<jats:p>In this work, p-type cuprous oxide (Cu2O) films grown on beta gallium oxide (β-Ga2O3) substrates by magnetron sputtering were reported. The resulting vertical Cu2O/β-Ga2O3 heterojunction p–n diodes demonstrated superior performance compared to devices fabricated with polycrystalline Cu2O thin films. Meanwhile, analysis of the discrepancies between the built-in potential and turn-on voltage revealed diverse carrier transport mechanisms in the fabricated devices. Numerical fitting of the forward J–V characteristics further discerned that distinct carrier transport mechanisms dominated under various bias voltages or temperature conditions. At 300 K, trap-assisted tunneling dominates the regime because of the presence of defects in β-Ga2O3 or Cu2O. While the bias voltage is low, the polycrystalline nature of the films formed at room temperature leads to the prevalence of grain boundaries as the primary source of interface-type defects at the Cu2O/β-Ga2O3 interface. Consequently, the dominant mechanism governing carrier transport is interface recombination. As the temperature increases, however, thermionic emission becomes more important. This study presents an opportunity for further investigation into the epitaxial growth of Cu2O and provides insights into the carrier transport mechanism of β-Ga2O3-based heterojunctions.</jats:p>