An ice shelter modular seating system includes a base unit, one or more seat mount units and one or more seat leg units. The base unit is a generally rectangular tub-like member having a front wall and a floor. The floor includes a longitudinally extending and integrally formed track. This track is functionally adapted to receive the lowermost portion of the seat leg units in it, the track being used to restrain the seat leg units from front to back movement relative to the base unit front wall. A seat mount unit is removably attachable to the base unit front wall and is configured to rest upon the seat leg unit. In this fashion, seat mount units can be positioned along the base unit as desired or required in an almost infinite number of positions and combination of positions, with placement of the seat mount units being be made quickly and easily.