A placket straightener device for minimizing buckling, gapping, or puckering of the overlapping placket panels on the ends of a shirt, such as a woman's blouse, when the fasteners, such as snap buttons or buttons with buttonholes, are fastened together. The device may be placed inside of the placket panel(s) or the device may be placed between two overlapping placket panels between the closed fasteners. The placket straightener device maintains a predetermined distance between the closed fasteners of the shirt thereby reducing buckling, gapping and puckering.