An embodiment of a preformed packaging sachet for receiving products, in particular food products, is provided with a closing device. The sachet has an opening bounded by a lip provided with an adhesive-coated strip, covered with a protective strip which is removed before adhesive-bonding to close the sachet. On the other side of the opening is another lip that is folded down against the outer face of the sachet as supplied, and that is intended to be folded up and adhesively bonded to the adhesive-coated lip in order to close the sachet.