A novel compact partial-H plane bandpass filter based on the composite right/left-handed (CRLH) transmission line in folded substrate-integrated waveguide (SIW) is proposed in this paper. The proposed filter consists of four identical CRLH resonators that resonate at the negative first-order resonant mode and occupy very compact physical sizes. Furthermore, the resonators were designed to be implemented in the folded SIW structure for suppressing the inherent fast-wave radiation phenomenon of the CRLH structure. As a result, the proposed filter combines the advantages of the CRLH structure for miniaturization and the SIW for high quality factors. Therefore, the resulted filter requires much smaller size as compared to the conventional SIW partial-H plane filter while exhibiting a much higher quality factor as compared to the conventional CRLH bandpass filters. A filter prototype with center frequency at 4.8 GHz was designed, fabricated and tested to demonstrate these features. Measured results agree well with the theoretical results.