A control device for a bicycle, has a first body adapted to be attached to a bicycle handlebar, at least one control member of at least one bicycle component, and a second body, distinct from the first body, connected to the first body to increase a grip surface of the control device and/or to vary the relative position of the at least one control member with respect to the handlebar of the bicycle, so as to adapt the control device to the size of the cyclist's hand.