This paper presents a dual-band filter using complementary split ring resonators (CSRRs) based on slow-wave substrate integrated waveguide (SIW) technology. Compared to conventional SIW the proposed topology includes internal metalized vias connected to the bottom metalized layer thus confining the electric fields in the upper layer, while the magnetic field is present throughout the whole substrate. By loading CSRRs on the top metal surface of this slow-wave medium, two pass bands propagating below the waveguide cutoff frequency can be generated. This novel topology allows relatively independent control over the centre frequency by tuning the internal metalized via heights and separation of CSRRs. Finite-element based electromagnetic simulations show that, the filter offers several advantages in terms of compact size, good selectivity and stopband rejection, as well as frequency tunability.