In this work, a metamaterial resonator based on complementary split ring resonator (CSRR) loaded with square open-loop resonator (OLR) is presented theoretically and experimentally. It is shown through equivalent circuit model that the addition of OLR to the conventional CSRR-loaded cell generates transmission zero in the upper stop band and improves the upper band rejection level without increasing the traversal dimensions. Simulation results show that a passband with high selectivity is obtained. Moreover, the via-free characteristic of the basic cell enables easy and low-cost fabrication.