An aircraft nacelle comprising a first and a second cowl mounted pivotably about an axis substantially parallel to a longitudinal axis of the nacelle and lockable to one another by at least one locking mechanism. The nacelle further comprises a device for providing a visual warning of a locking defect of the cowls. The device comprises a movable bolt associated with the locking mechanism and a movable edge plate mounted on the nacelle in line with said bolt with which it is associated, the movable edge plate being movable under the action of an operator between a protruding position, in which the edge plate is protruding from the nacelle and a locking mechanism is in an unlocked position, and a retracted position, in which the edge plate is immobilized within the nacelle by the bolt and the action of the locking of a locking mechanism.