A unit for the glue application of at least two labels to containers, comprising at least one first application device (8) and one second application device (9) both of which rotate and are positioned at two separate superposed portions of the main axis of rotation (Z), each for applying at least one label on a separate portion of the same container (2). In practice, the operating parts of the two application devices (8) and (9) are at different distances from the axis of rotation (Z), although they rotate at identical rotational speeds relative to said axis. The second application device (9) comprises two first follower elements (30) which are slidably connected to a stationary first guide element (29), for guiding the movement of the second device in space. At least at the label application position (24), the interaction between the first follower elements (30) and the first guide element (29) causes an oscillation of the second application device (9) for varying the speed of movement of its operating part and adapting it to that of the container to be labelled.