In a hybrid outboard motor equipped with an internal combustion engine and electric motor as selective sources of power for driving the propeller and further provided with the first output shaft connected to the engine for transmitting its output to the propeller and the second output shaft connected to the motor for transmitting its output to the propeller, the first and second output shafts are disposed coaxially, so that the amount of space required for installing the shafts is smaller by the length of their coaxial portion relative to the prior art in which the shafts are simply connected in tandem. As a result, the size and weight of the outboard motors can be reduced, thereby enhancing its ease of operation and portability.