A window security assembly includes a plurality of first brackets that is each mountable on a window in a wall of a building. A plurality of second brackets is each mountable on the window in the wall of the building. A plurality of fasteners is each extended through a respective one of the apertures in a respective one of the first brackets and the second brackets. In this way the first brackets and the second brackets are coupled to the window. A panel is positionable in the first brackets and the second brackets when the first brackets and the second brackets are positioned on the window. The panel is comprised of an impact resistant material to inhibit an intruder from gaining access through the window.