A device and method for sealing an inflated balloon includes providing a balloon-tying pump nozzle that has an air nozzle defining an air passageway adapted for communicating air between an air-collection chamber of an air pump and the environment and a balloon-neck-engaging extension adjacent to and extending substantially parallel to the air nozzle, the balloon-neck-engaging extension defining a channel between the balloon-neck-engaging extension and the air nozzle, wherein the channel is sized to accept a neck of a standard party balloon therein while inhibiting a lip of the standard party balloon from passing therebetween. The method further includes the steps of placing a neck of a balloon adjacent the air nozzle and the balloon-neck-engaging extension so that the balloon is on a first side of the air nozzle and the balloon-neck-engaging extension, securing a portion of the neck of the balloon with reference to the air nozzle, manipulating the balloon so that at least a portion of the neck of the balloon is wrapped completely around both the air nozzle and the balloon-neck-engaging extension, inserting a portion of the neck within the channel so that the lip of the balloon is on a second side of the air nozzle and the balloon-neck-engaging extension, and removing the balloon from both the balloon-neck-engaging extension and the air nozzle, thereby causing the balloon to form a knot.