Cortactin is an F-actinâ€"binding protein that localizes to the cell cortex, where the actin remodeling that is required for cell migration occurs.We found that cortactin shuttled between the cytoplasm and the nucleus under basal conditions. We identified Kelch-like ECH-associated protein 1 (Keap1), a cytosolic protein that is involved in oxidant stress responses, as a binding partner of cortactin that promoted the cortical localization of cortactin and cell migration. The ability of cortactin to promote cell migration is regulated by various posttranslational modifications, including acetylation. We showed that the acetylated form of cortactin was mainly localized to the nucleus and that acetylation of cortactin decreased cell migration by inhibiting the binding of cortactin to Keap1. Our findings reveal that Keap1 regulates cell migration by affecting the subcellular localization and activity of cortactin independently of its role in oxidant stress responses.