This system (S) for tensioning a racket string (C) comprises a traction module (1) suitable for exerting a traction force (T) on a string (C) of a racket, including a grip (3) comprising two opposite jaws (32) suitable for gripping the string (C) between them when it is tensioned, and a traction head (5) on which the grip (3) is mounted, the jaws (32) being translatable simultaneously relative to the traction head (5) and arranged such that the translation of the jaws (32) causes them to tighten around the string (C), a rail (7) on which the traction head (5) of the traction module (1) is mounted translatably, and a traction motor able to translate the traction head (5) of the traction module (1) on the rail (7), via a driving system (13). The system comprises means (15) for transmitting movement between the driving system (13) of the traction head (5) and the jaws (32), this transmission means being able to initiate the translation of the jaws (32) relative to the traction head (5) in the direction gripping the string (C).