K(V)10.1 is a voltage-gated potassium channel aberrantly expressed in many cases of cancer, and participates in cancer initiation and tumor progression. Its action as an oncoprotein can be inhibited by a functional monoclonal antibody, indicating a role for channels located at the plasma membrane, accessible to the antibody. Cortactin is an actin-interacting protein implicated in cytoskeletal architecture and often amplified in several types of cancer. In this study, we describe a physical and functional interaction between cortactin and K(V)10.1. Binding of these two proteins occurs between the C terminus of K(V)10.1 and the proline-rich domain of cortactin, regions targeted by many post-translational modifications. This interaction is specific for K(V)10.1 and does not occur with K(V)10.2. Cortactin controls the abundance of K(V)10.1 at the plasma membrane and is required for functional expression of K(V)10.1 channels.