A stairway system, kit and method for assembling the kit are provided, the system including pre-fabricated components such as steps, stringers, decorative moldings and panels or boards, etc., on site. The kit comprises a step module and an adjacent step module, the step module comprising a riser and a tread, the riser being adapted to abut the tread on a first side thereof and being adapted to define a fastener-mating portion on a second side thereof. The tread is adapted to be secured atop the riser on one side thereof. The adjacent step module comprises a riser and a tread, the adjacent step module being adapted to be assembled with the step module by engaging a fastener with the fastener-mating portion of the step module and securing the fastener to the tread of the adjacent step module to secure the two step modules together.