In this paper, a novel approach to design triple-mode SIW filter is proposed. A rectangular SIW cavity with two degenerate modes and the complementary split ring resonators (CSRRs) etched on the top plane of this cavity are combined to implement a triple-mode filter. The filter has high out-of-band rejection and sharp skirt selectivity due to three transmission zeros appearing. Another advantage of this method is that the operating bandwidth of this filter can be controlled by changing the external dimensions of CSRRs and the position of the perturbed metallic vias. Finally, an example of triple mode filter is given and the measured results show its good performance. © 2016 IEEE.