In this work, a millimeter wave (mm-wave) bandpass filter consisting of six resonant cavities for 5G communication is designed on the basis of a substrate-integrated waveguide (SIW). The bandpass characteristics of the SIW filter are achieved through magnetic coupling, which is accomplished by adjusting the size of the openings between neighboring resonant cavities. The measured fractional bandwidth is 3.56% (24.8–25.7 GHz), with an insertion loss of 0.88 dB at the center frequency of 25.25 GHz, and the in-band return loss is better than 12 dB. The simulated results of this filter show excellent agreement with the measured results. It exhibits low loss, simple structure, low cost, ease of integration with other electromagnetic systems, including sensor systems, and suitability for use in 5G mm-wave bands.