A control device for controlling a pedal-assisted bicycle comprising a pedal-thrust group , a transmission operatively interposed between said pedal-thrust group and at least one wheel and a free-wheel mechanism associated with said at least one wheel , said control device comprising: - an electric motor associated with a wheel of the bicycle ; - at least one battery pack associated with said motor so as to bidirectionally exchange energy with it; - first sensor means configured to detect at least one quantity correlated with the speed of one wheel of the bicycle and to generate one or more signals representing this at least one quantity; - at least one control unit associated with said first sensor means and with said motor and configured to drive the electric motor at least according to one operating modality, wherein it acts as an actuator or generator as a function of the angular velocity of the wheel ; wherein said control unit is further configured to drive the electric motor according to an anti-theft modality, wherein said motor imparts a torque opposite to a direction of rotation of the wheel as detected by the first sensor means , and wherein, in the anti-theft modality, the control unit is configured to drive the motor alternatively in a passive configuration, wherein the motor does not require energy from the battery pack , or in an active configuration, wherein it imparts said torque opposite to a direction of rotation of the wheel and requires energy from the battery pack , characterised in that in the anti-theft modality, the control unit is configured to drive the motor in the passive configuration under a preestablished speed limit for the bicycle and to drive the motor in the active configuration over said speed limit. - an electric motor associated with a wheel of the bicycle ; - at least one battery pack associated with said motor so as to bidirectionally exchange energy with it; - first sensor means configured to detect at least one quantity correlated with the speed of one wheel of the bicycle and to generate one or more signals representing this at least one quantity; - at least one control unit associated with said first sensor means and with said motor and configured to drive the electric motor at least according to one operating modality, wherein it acts as an actuator or generator as a function of the angular velocity of the wheel ; wherein said control unit is further configured to drive the electric motor according to an anti-theft modality, wherein said motor imparts a torque opposite to a direction of rotation of the wheel as detected by the first sensor means , and wherein, in the anti-theft modality, the control unit is configured to drive the motor alternatively in a passive configuration, wherein the motor does not require energy from the battery pack , or in an active configuration, wherein it imparts said torque opposite to a direction of rotation of the wheel and requires energy from the battery pack , characterised in that in the anti-theft modality, the control unit is configured to drive the motor in the passive configuration under a preestablished speed limit for the bicycle and to drive the motor in the active configuration over said speed limit. <EOS>