In this paper, a dual-band bandpass filter is proposed in substrate integrated waveguide (SIW) technology. A single cavity that supports both TE101 and TE201 resonating modes is used for the design. The two passbands are created by the two modes. To improve the selectivity, one bypass coupling path is introduced which provides additional transmission zero. The procedures to control the passband center frequencies as well as their bandwidths are presented. A prototype narrowband bandpass filter with the center frequencies of two passbands as 10 GHz and 11 GHz is fabricated for space applications. The 3 dB fractional bandwidths are 3% and 1.6%, respectively. The measured insertion losses at the passband center frequencies are 1.4 dB and 2.6 dB, respectively. © 2016 IEEE.