In arterial myocytes, the canonical function of voltage-gated Ca_V1.2 and K_V2.1 channels is to induce myocyte contraction and relaxation through their responses to membrane depolarization, respectively. Paradoxically, K_V2.1 also plays a sex-specific role by promoting the clustering and activity of Ca_V1.2 channels. However, the impact of K_V2.1 protein organization on Ca_V1.2 function remains poorly understood. We discovered that K_V2.1 forms micro-clusters, which can transform into large macro-clusters when a critical clustering site (S590) in the channel is phosphorylated in arterial myocytes. Notably, female myocytes exhibit greater phosphorylation of S590, and macro-cluster formation compared to males. Contrary to current models, the activity of K_V2.1 channels seems unrelated to density or macro-clustering in arterial myocytes. Disrupting the K_V2.1 clustering site (K_V2.1_S590A) eliminated K_V2.1 macro-clustering and sex-specific differences in Ca_V1.2 cluster size and activity. We propose that the degree of K_V2.1 clustering tunes Ca_V1.2 channel function in a sex-specific manner in arterial myocytes.