A device for inserting wires and/or pipes in a tubular, flexible sheath includes a sleeve (11), with a split (111) made therealong. The sleeve (11) is encircled by a cylindrical tubular body (21) also having made therealong a relative split (211). The sleeve (11) can turn inside this cylindrical tubular body (21), so as to define two working positions, first (H1) and second (H2). In the first working position (H1), the split (111) of the sleeve (11) corresponds to the split (211) of the tubular body (21), so that the wires can be inserted into the device. In the second working position (H2), the split (211) of the tubular body (21) is closed by the sleeve (11), so as to block the wires inside the device. A rounded, wedge-shaped member (23) rising over the cylindrical tubular body (21) is to be slidably fitted in the flexible sheath (F). The profile of the member (23) allows to open the edges of the elements (3) of the sheath, so as to insert the wires thereinside.