The self-mounting and collapsible tray has a base (1), two side walls (2) and two end walls (3), as well as, in correspondence with each corner, a corner pillar which comprises at least four segments (41-44) separated by fold lines (4a-4c).The last segment (44) is affixed to the end wall so that at least one part of the last segment extends from one of the intermediate segments (43) and toward the center of the end wall, distancing itself from the corresponding corner of the tray. In addition, the tray comprises, in correspondence with each end wall (3), a transversal flap (5) constituted by at least one part of a prolongation of the end of the end wall which corresponds to the upper part of the end wall of the tray in the erect position, said transversal flap (5) having two ends (51), each folded over and affixed to an outside face of the corresponding side wall (2).