Tibicen pruinosus (Say)—a large, arboreal cicada typically found in the central United States—is reported for the first time from Colorado. This new state record represents a significant western extension of this cicada's known range. Also reported are new records from Kansas that link the Colorado population to the previously known distribution of T. pruinosus. These results suggest that T. pruinosus has expanded its range westward, likely facilitated by human-induced changes in vegetation on the Great Plains. They also indicate the effectiveness of acoustic surveys as a tool for studying cicada distributions. Finally, an updated key including all 7 species of Tibicen now known from Colorado is provided.