An anti-theft display case for manufactured products; in particular, display cases that can be opened and re-closed to contain the product to be displayed and provided with means of maintaining the case closed up to completion of sale, so as to prevent the unauthorized removal of the product. The anti-theft display case is provided with at least one first portion and one second portion, one mobile in relation to the other between an open and a closed position, and a means of locking said portions in the said closed position. The second portion is formed from at least two pieces bound one to the other and mobile one in relation to the other telescopically to increase the volume of the display case.