Disclosed is a method and device for detecting lateral dissymmetry of an aircraft. A control parameter determination unit is used to determine a current value of a control parameter representative of all roll control surfaces of the aircraft, and a control parameter comparison unit is used to compare the determined current value with a predetermined reference value. A current deflection angle of a lateral stick of the aircraft is also determined, and the determined current deflection angle is compared with a predetermined angle value. A visual alarm signal is output, when the current value of the roll control surfaces of the aircraft is greater than a predetermined reference value and the lateral stick is at a deflection angle that is greater than a predetermined angle value.