High-level ab initio quantum calculations were performed to study thirteen and sixteen low-lying electronic states of ZrO+ and NbO+. We report their potential energy curves, electronic configurations, bond distances, harmonic vibrational frequencies, anharmonicities, spin–orbit splittings, and excitation energies. Chemical bonding patterns for low-lying electronic states are also proposed. The removal of one electron from the ~5sZr of ZrO creates the first three states of ZrO+ (X2Δ, 12Σ+, 12Π). These three states bear oxo (Zr3+O2−) character and the remaining states show oxyl (Zr2+O·−) nature. Similarly, the detachment of one electron from ~5sNb of nine low-lying states of NbO generate the nine lowest energy states of NbO+ that possess oxo (Nb3+O2−) character. Low-lying electronic states of ZrO+ and NbO+ are very similar to their isovalent TiO+ and VO+ partners. The current study rectifies spectroscopic assignments made for ZrO+ and NbO+ in the literature.