This SEER-based ecological study examined U.S. trends (2000–2021) in malignant and benign brain tumor incidence and compared them with national mobile phone subscription trends. Malignant brain tumor incidence in adolescents and adults declined slightly, while benign brain tumor incidence increased over time; temporal lobe tumors and benign acoustic neuromas showed little change. The authors interpret these patterns as not supporting an association between mobile phone use and increased brain cancer risk, while recommending continued surveillance given rising benign tumor incidence and potential latency.