In this paper, the displacement of the phase centers of multi-mode antennas is investigated. A mathematical approach is applied in order to calculate the positions of the phase center for each mode. Using electric far field samples obtained from electromagnetic field simulation data, the coordinates of the shifted positions of the phase center relative to the physical center of the antenna are determined for each mode. Numerical results show the dependency of the phase centers of an antenna prototype as a function of the considered angle of observation.