A modular seating system is provided having one or more seat units that are connectable to each other by connection plates. The seat units include first connector components for connection to back units and/or arm units. The back units and arm units include second connector components configured to cooperate with the first connector components. The arm units are provided with two sets of the second connector components for connecting to the seat unit in a first position or a second position different than the first position. The first and second connector components are in the form of a rail and C-shaped bracket that can slide over the rail.