The invention relates to a yaw control device for an aircraft fitted with a supersonic nozzle having a rectangular or flat section comprising a supersonic throat extended by a diverging portion in which supersonic flow occurs. In order to enable the aircraft to be controlled in yaw in the absence of a vertical fin, the device of the invention makes use of jet control surfaces in the form of airfoils disposed in the diverging portion of the nozzle. The control surfaces are movable about respective pivot axes in order to generate a lateral force when in a deflected position, so as to enable the aircraft to turn about its yaw axis.