A ±45° dual-polarized antenna is designed based on the gap waveguide technology which offers a low loss and easy-to-manufacture solution at the mmWave frequencies. Dual-polarized antennas help to increase the capacity and coverage of a wireless system and also decrease the overall cost. Two parallel arrays of 8 slots each are employed to create the orthogonal polarizations. The antenna operates in the 24.25 − 27.25 GHz frequency band. The simulated average gain of each polarization is 14.5 dBi while achieving a cross-polarization isolation of at least 15 dB.