Described is a device for synchronization of a reverse gear for a vehicle gearbox including: a support shaft fixed in rotation; an idle gear wheel for engagement with a first reverse gear wheel on a gearbox primary shaft and a second reverse gear wheel on a gearbox secondary shaft, said idle gear wheel mounted rotatable and axially slidable on said support shaft and having a hub including a first friction surface; and a synchronizer ring mounted mobile on said support shaft along an axial travel and countered axially by an elastic element along said axial travel, said synchronizer ring having a second friction surface for engagement with said first friction surface. Axial movement of the idle gear wheel towards an engagement position of the reverse gear causes drawing of the synchronizer ring implementing, prior to reverse gear engagement, braking of rotary movement of the idle gear wheel.