Abstract: An under deck drainage system for a fluidly pervious deck of light frame construction provides paired spacedly opposed elongate fastening brackets, carried on adjacent surfaces of opposed pairs of deck supporting joists, with a downwardly curving drainage panel extending therebetween to receive and transport drainage to a deck edge perpendicular to the joists. The fastening brackets are sealed against the joists carrying them and provide two vertically spaced fastening arms that sealably engage the edges of the drainage panel carried therebetween in a releasable, positionally maintainable interconnection of opposed tooth-like fastening ridges carried by the drainage panel edges and the fastening arms.