A device for pneumatic knotless splicing of ends of thread or yarn. There is provided a cylindrical cavity, which is connected to a source of compressed air. In the cylindrical cavity, a piston rod is displaceable in both directions. A piston rod is actuated by an actuation lever, from a cam track of a drum. The track is divided at one section into two parallel branches. A first branch is used during rotation of the drum in a forward direction to displacement of the rod in one direction. A second branch is used during rotation of the drum in a return direction to displacement of the rod in the opposite direction. The cylindrical cavity with the piston rod constitutes a slide valve, for introducing compressed air into the devices for preparation of the ends of thread or yarn to be joined, when the rod is actuated in order to be displaced in the one direction, and to introduce the compressed air into the splicing chamber, when the rod is actuated in order to be displaced in the opposite direction, for execution of the pneumatic splicing of the two ends of thread or yarn. A specific amount of free play is provided in a lever transmission between the cam with an increasing profile and the drawing levers. The drawing levers are provided with braking means, to keep them stopped in the displaced position, on completion of the forward rotation of the drum.