A floor drain system includes a generally rectangular drain grate having a plurality of drain apertures, and a drain body, having a circular lower portion defining an outlet and configured to mate with an underdrain structure, and an upper portion defining an inlet configured to receive the drain grate in a frictional fit. The drain body includes an integral grout rim surrounding the inlet, having a knife-tapered top edge, configured to reduce the visibility of the grout rim between the surrounding material and the grate. The drain body further includes an undercut rim around an outer perimeter of the inlet, the undercut rim having a bottom surface angled upward toward the drain body. The drain body can also include dovetail-shaped buttresses extending outward from the drain body, having tapered surfaces angled toward the drain body, thereby to mechanically interlock the drain body with hardened grout therearound.