Density functional theory (DFT) calculations are performed to study the Y4O molecule in its neutral, anionic, and cationic states. The equilibrium geometries of Y4O, Y4Oˉ, and Y4O+ are trigonal bi-pyramids. The ground states of Y4O, Y4Oˉ, and Y4O+ are triplet (3A1), doublet (2A00), and doublet (2A0), respectively. Time-dependent DFT is used to calculate the excited states. A theoretical assignment for the features in the experimental photoelectron spectrum is given. All results obtained are in good agreement with the available experimental data.