The invention relates to a device for tensioning the retractable top of a motor vehicle (1). Said top comprises a front element (2) and a rear element (3) which are displaceable between the closed and opened positions thereof. The displacement of said elements is controlled by two articulated arms (6, 7). The inventive device is provided with arresting means (9) carried by the first arm (7) in such a way that is abuts against the second arm (6) when two elements (2, 3) of the top are relatively near to the closed position thereof. The arresting means (9) are provided with elastic means able to resist to the relative motion of the arms (6, 7) when the elements of the top (2, 3) are displaced from the relative position thereof, which is near to the closed position, and move towards said closed position.