In this article, a novel planar multilayer Q‐band band‐pass filter is presented by cascading a low‐pass filter (LPF)and a high‐pass filter (HPF). The HPF is designed by utilizing the high‐pass behavior of the substrate integrated waveguide, and the LPF is realized by using millimeter‐wave lump‐element resonators. Since the insertion loss resulted by the millimeter‐wave planar resonators, which resonate in‐band and have a limited quality factor, is avoided by using the cascaded high‐/low‐pass architecture, the proposed filter has a small insertion loss. Moreover, a flexible bandwidth can be achieved by properly adjusting the cutoff frequencies of the HPF and LPF. As a demonstration, a band‐pass filter having a center frequency of 42.5 GHz and a fractional bandwidth of 11.76% is designed, fabricated, and measured. Good agreement is obtained between simulated and measured results. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:698–703, 2017