A temperature- and pH-responsive drug delivery system was studied by using interpenetrating polymer network (IPN) hydrogels constructed with poly(acrylic acid) (PAAc) and poly(vinyl alcohol) (PVA). The release of indomethacin incorporated into these hydrogels showed pulsatile patterns in response to both pH and temperature. Indomethacin diffused from the polymer matrices through the swelling and deswelling mechanism. The release amount increased at higher temperature because of the swelling caused by the dissociation of hydrogen bonding. The drastic change of drug release was achieved by alternating pH of the buffer solution and was attributed to the change of states of ionic groups within IPN hydrogels. The free water contents were calculated by using differential scanning calorimetry (DSC), and were proved to be the main factor in the swelling. These results demonstrated that the drug release could be controlled by the swelling/deswelling degree of IPN hydrogels as functions of pH and/or temperature.