In January 2008, Wagner competed on the senior level for the first time at the 2008 U.S. Nationals in St. Paul, Minnesota. She placed second in the short program behind Mirai Nagasu after landing a triple Lutz-triple loop combination. In the free skate, she placed second again, this time behind Rachael Flatt, after landing seven triples including another triple Lutz-triple loop combination. She finished with the bronze medal overall behind Nagasu and Flatt. Because Nagasu, Flatt, and pewter-medalist Caroline Zhang were too young to compete at an ISU Senior Championship event, Wagner was the only medal winner to be named to the Four Continents and World Championships teams. Because of her third-place finish at the 2008 Nationals, Wagner earned a bye to the 2009 U.S. Nationals.