—In this paper, novel bandpass filter and tunable bandpass filter are designed based on half-mode substrate integrated waveguide (HMSIW) embedded with complementary resonators. Various passband characteristics are observed, and lumped equivalent circuit analysis models are developed. The configuration of the proposed bandpass filter is an open structure, and it is easy to load the active devices and build the bias/control networks on the signal plane. The tunable bandpass filter is presented based on the proposed novel bandpass filter loaded with semiconductor varactor diodes, and it has good spurious suppression characteristics and excellent out of band rejection. The prototype with overall size of 15.9 mm × 30.2 mm × 0.5 mm was designed and fabricated so as to validate the new structure. The measured central frequency is 1.538 GHz and 1.718 GHz, and the insertion loss is 5.1 dB and 3.3 dB, at 0 V and 30 V, respectively.