A tubular electromechanical actuator includes an electric motor, reduction gear, output shaft and casing. The casing is hollow and houses at least the electric motor and the reduction gear. The casing includes a first end and a second end. The actuator also includes a retaining element assembled at the first end of the casing, so as to close off the first end of the casing. The retaining element includes at least a first stop configured to cooperate with the reduction gear, in an assembled configuration of the actuator, and a second stop configured to cooperate with the casing, at the first end of the casing, in the assembled configuration of the actuator. Furthermore, the retaining element includes at least one accommodation configured to cooperate with at least one rib of the reduction gear, so as to participate in the sealing between the retaining element and the reduction gear.