Abstract The electronic structure of copper phthalocyanine (CuPc) monolayer was investigated by the first-principles all-electron full-potential linearized augmented plane wave (FLAPW) energy band method. The magnetic properties of the CuPc monolayer were investigated with spin-polarized calculation. It was found that the Cu atom has a magnetic moment of 0.56 μ B, but it does not affect strongly the paramagnetic properties of the monolayer. The ground-state electronic structure of the CuPc monolayer found in spin-polarized calculation is indistinguishable from the paramagnetic case in the energy range from −10 to −1.5 eV and above 1.0 eV, with respect to the Fermi level ( E F), but taking into account the magnetic properties of the open-shell Cu atom results with the splitting of bands near E F . The obtained total density of states and the calculated values of work function (4.66 eV) and ionization potential (5.23 eV) of the CuPc monolayer were found to be in a good agreement with the experimental data concerned CuPc thin films.