A window insertable pet door devised for removable installation in a window without tools and without altering the window by including a center frame having a U-shaped bracket on a top side thereof and a pair of side panels that slidingly extend from the center frame to engage a bottom railing and a respective one of a right railing and a left railing of a window frame. Each side panel includes an outer trim and a static barrier wall therewithin formed of a plurality of vertical popoid pleats. An annular door frame is centrally disposed in the center frame, with a gasket being disposed between the door frame and the center frame. A plurality of pliable triangular flaps, radially disposed within the door frame, converge at a center point of the door frame to simultaneously fold inwardly and outwardly for passage of a cat therethrough.
