A mounting system for a recessed luminaire includes an upper frame 200 to fit within a cutout opening 141 in a ceiling 140, including pivotally mounted support levers 202 to overlap the upper surface of the ceiling. A lower frame 210 fits within the opening and has a trim face 220 that is configured to abut against the room-side surface of the ceiling. Clamping screws 212 fasten the lower frame to the upper frame and are adjustable to clamp varying thicknesses of ceilings between the support levers and the trim face when the screws are tightened. Fasteners 132 fasten a luminaire 100 to the lower frame, which is installed through the lower and upper frames, from the room-side of the ceiling. The mounting system and luminaire may be completely installed from below a ceiling that has limited space above the ceiling or when access above the ceiling is not available.