This paper investigates the effects of inter-resonator coupling in metamaterial transmission lines loaded with split ring resonators (SRRs). The study is performed from Bloch mode theory applied to the multiport equivalent circuit model of the unit cell of such artificial lines. From this analysis, it follows that the stopband bandwidth, inherent to SRR-loaded lines, is enhanced as inter-resonator coupling strengthens, and this enhancement is attributed to the presence of complex modes. The theoretical results are corroborated through calculation of the dispersion relation using a full-wave eigenmode solver, and also by measuring the frequency response of SRR-loaded lines with different inter-resonator distance and, hence, coupling. © 2014 AIP Publishing LLC.