A collapsible cage, which comprises a bottom that is surmounted by, and associated with, grid-like walls mutually connected by connection comprising, for each corner, a corner joint constituted by a main element, with a concave corner body in which positioning seats are provided for three converging grid-like walls, and at least one locking element for the three grid-like walls in the positioning seats. The locking element is formed monolithically with the main element and is further deformable in order to be arranged in the locking configuration.