A method of making a balloon includes providing two balloon films and providing two valve films. The two valve films are placed one on top of the other and then inserted between the two balloon films. Then a portion of each of the valve films is tack sealed to its respective adjacent balloon film. The valve films are then sealed together to form a valve passageway therein. During the valve sealing step, the balloon films are held in a fanned out manner. Finally, the balloon films are sealed together along the perimeter thereof to form the balloon.