A modular step system for in-ground swimming comprising a bottom central hub, a brace assembly, a top central hub, a tread support assembly, a step form and a liner. The components of the modular step system interlock and snap together without fasteners. Also, the components of the modular step system are obtained by molding plastic material or curing of a curable material. The modular step system is installed on a level concrete floor of a swimming pool and designed to be rigidly fixed from behind to adjacent pool walls. The modular step system is adaptable to a pool having a vinyl liner, structurally sound regardless of size, easy to assemble, consistent in size, and cost-effective.