Described herein is a device for opening hermetic flexible containers (1), comprising a flexible strip (7) heat-sealed to the internal surface of a wall (3) of the container (1) and incorporating a tape-like thread (9) having a tear tab (10) to cause tearing of the strip (7), and the consequent tearing of the wall (3) of the container (1), via a gripping tab (5) of said wall (3). The gripping tab(5) and tear tab (10) are staggered with respect to one another and hermetically isolated by a heat seal (19) between the strip (7) and the wall (3) of the container (1).