The invention relates to a tailgate of a motor vehicle having at least one side post to which a window is added, the post constituting a U-shaped profile member with an open cross-section, in which the opening is turned towards the window, the profile member including a base provided with a first side flank and a second side flank. The second flank includes a trim which curves, opposite the Y0 of the vehicle, towards the first flank so as to at least partially close the opening of the profile member, the trim being added to the second flank without reducing the rear field of vision.