In this paper, a simple parallel-coupled band pass filter with a metamaterial complementary split ring resonator is introduced for improvement of the filter stopband attenuation. The theoretical concept of the complementary split ring resonator is introduced. The designed filter has been examined theoretically using circuit modelling and electromagnetic full wave simulation. The results demonstrate that the reported filter can enhance the stopband attenuation three times compared to conventional filter with maintaining typical linear phase response and constant group delay. Moreover, these results have been obtained using only one unit cell for the sake of filter compactness and simplification.