The disclosure relates to an electric motor including a support block containing a ball bearing housing, a rotor that projects from this housing, and a stator assembly mounted around said rotor and fastened on said support block, characterized in that an annular seal, preferably of O-ring type, is squeezed between said stator assembly and the periphery of the fixed race of said ball bearing, the pressure of said annular seal preventing axial and rotational movement of said fixed race; the invention also proposes an assembly process for such an electric motor. The invention is notably suitable for sealed rotor motors.