In immune cells, the activation of K⁺ channels causes membrane hyperpolarization and Ca²⁺ increase through voltage-independent Ca²⁺ channels, thus controls various cellular functions. The inward rectifier K⁺ channel Kir2.1 has been reported to be functionally expressed in leukocytes, but its physiological significance is unclear. This study was undertaken to elucidate the physiological roles of Kir2.1 channels in macrophage functions using mouse bone marrow-derived macrophages (BMDM). Whole-cell patch-clamp recordings revealed that Kir2.1 channels were responsible for inward rectifier K⁺ currents in BMDM. Membrane hyperpolarization by the activation of Kir2.1 channels promoted store-operated Ca²⁺ entry (SOCE) through Ca²⁺ release-activated Ca²⁺ (CRAC) channels in BMDM treated with thapsigargin or ATP. Migration experiments by scratch assay demonstrated that the activities of both Kir2.1 and CRAC channels enhanced cell migration. In addition, the cell migration was significantly inhibited by an inhibitor of Ca²⁺/calmodulin-dependent protein kinases (CaMK). These results suggest that Kir2.1 channels activate CaMK and promote cell migration by increasing SOCE through CRAC channels in BMDM. Kir2.1 channels may enable efficient migration of macrophages to damaged or/and inflamed sites and be involved in cell defense mechanisms.