An electronic control unit included in a control system is configured to execute a change of a combustion mode in an inertia-phase period during a gear shift operation, or after the gear shift operation is completed, when a request for the change of the combustion mode and a request for a gear shift of the transmission mechanism overlap. The electronic control unit is configured to execute the change of the combustion mode in the inertia-phase period during the gear shift operation when conditions i) and ii) are established, and execute the change of the combustion mode after the gear shift operation is completed when conditions i) and iii) are established. The aforementioned conditions include: i) the change of the combustion mode is accompanied by an increase in engine power; ii) the power running mode is executed during the gear shift operation; and iii) the regeneration mode is executed during the gear shift operation.