A substrate integrated waveguide (SIW) equipped with moats is investigated in this paper. Different from the commonly used SIW having dense via holes, this new SIW employed sparse via holes incorporating moats outside the via-hole arrays. Through numerous experimental studies, we found that it can maintain high transmission characteristics by introducing additional moats outside the via-hole arrays. Moreover, it is interesting to notice that such a new structure can lower its cutoff frequency and thus increase its operation bandwidth. Additionally, the calculation for the dispersion relation of such a new waveguide was carried out to understand its wave-guiding characteristics.