A jet engine nacelle has one thrust reverser device which includes a deflection means and one cowl translatable in a direction substantially parallel to a longitudinal axis of the nacelle. The cowl can translate between a closed position and an open position. In the open position, the cowl ensures the aerodynamic continuity of the nacelle and covers the deflection means. In the open position, the cowl opens a passage into the nacelle and uncovers the deflection means. The thrust reverser device moreover includes one blocking flap pivotably mounted by one end attached to a rear portion of the deflection means, and slidingly connected to the moving cowl. The pivoting end is also translatably connected to the rear portion of the deflection means.