The electronic structures of tetragonal palladium oxide (PdO, space group P4₂/mmc) were calculated using the first-principles DFT+U and DFT+U+V methods. The calculations gave the band gap that reproduced the experimental values. It was found that the conduction band comprised the anti-bonding interactions of Pd 4d_zx–O 2p and Pd 4d_zx–O 2s, whereas the valence band top mainly comprised the anti-bonding interactions of Pd 4d_z2–O 2p and Pd 4d_x2-y2–O 2p. The DFT+U+V method, compared with the PBE and HSE06 functionals, gave larger Pd–O interactions near the valence band top. The electronic structures of rock salt PdO in the type-II antiferromagnetic phase were also computed as a comparison with nickel oxide (NiO).