Interleukin 32 (IL-32) is a recently identified cytokine that induces major proinflammatory cytokines such as $TNF{alpha}$ and IL-$1{eta}$, which play an important role in chronic inflammatory diseases. To antagonize the biological function of IL-32 in cells, we generated RNA aptamers that could bind specifically to IL-32 protein. The highest affinity aptamer, AC3-3, successfully antagonized IL-32 by abolishing the induction of $TNF{alpha}$ in the human lung carcinoma cells expressing IL-32. This aptamer could be used as a potent and selective antagonist against IL-32 to further elucidate the roles of IL-32 in chronic inflammatory diseases, as well as a therapeutic agent.