A sprocket of a chain transmission for a bicycle is described, intended to be coupled with a further sprocket with a smaller diameter in a group of sprockets integral in rotation. The sprocket comprises a plurality of teeth which follow each other on the sprocket separated by spaces according to a direction of rotation of the sprocket, in which each tooth has a thickness, a width and a height and has a lead side, a following side, a front side and a rear side. The sprocket has a front bevel on at least one tooth of first disengagement of said plurality of teeth and a rear bevel (60) on at least one tooth of last engagement of said plurality of teeth.