An outboard motor steering system for an outboard motor mounted on a stern of a boat includes a mounting unit having a swivel shaft connected to a propeller to turn the propeller, and a swivel case rotatably accommodating the swivel shaft. A vibration attenuator is installed at a portion connecting an outboard motor main unit and the mounting unit and attenuating vibration of the outboard motor main unit to be transmitted to the mounting unit by causing the outboard motor main unit to displace relative to the mounting unit. In the system, displacement absorbers are installed at a portion connecting one of a main body and an output end of a steering actuator to the outboard motor main unit and another portion connecting the other of the main body and the output end to the mounting unit.