A power unit for a motorcycle includes an internal combustion engine provided with a crankcase rotatably supporting a crankshaft with an axial line extending in a vehicle-width direction. An oil pump is mounted on the crankcase with a balancer rotatably supported by the crankcase. Rotational power from the crankshaft is transmitted to a pump driven member provided on a pump shall of the oil pump and to a balancer driven member coaxially interlinked with and connected to the balancer so as to transmit power to the balancer. The power unit is downsized by bringing a balancer and an oil pump into a close arrangement. The pump driven member and the balancer driven member are offset from each other in a vehicle-width direction and are located at such a position so as to at least partially overlap each other as viewed from the side of the vehicle-width direction.