Abstract: A window shelf system includes a pair of elongate shelf mounting tracks, each track defining a plurality of notches. An upper support arm is attached to the back side of each track adjacent a top thereof, each upper support arm having a downwardly extending flange for insertion between an upper trim molding segment and a wall such that the mounting tracks may be hung from the trim typically mounted to a wall above a window. Shelf support arms releasably mate with the notches for selectably determining a height for supporting a shelf board thereon. Length-adjustable lower support arms are attached to back sides of respective tracks adjacent a bottom thereof for displacing lower ends of the tracks from the wall. Each mounting track includes a telescopic support leg which may be extended to support the weight of the system and articles placed on the shelf board.