Abstract: A vent window lock assembly for securing a pivotable vent window having a vertical edge at one end to a vertical window post having a wing flange against which said end of the vent window resides when the window is closed, is disclosed. The lock assembly includes an S-shaped bracket, a hook plate, and a fastener. The S-shaped bracket defines opposed first and second overlapping channels. The first channel is adapted for gripping the vertical edge of the vent window, with the end portion of the bracket that defines the first channel being for positioned on the outside of the vent window. The second channel is adapted for gripping the wing flange of the window post, with the end portion of the bracket that defines the second channel being positioned on the inside of the window post. The hook plate is slidably fastened to the end portion of the bracket that defines the second channel.