An 83-year-old woman with RET fusion-positive advanced lung adenocarcinoma was administered selpercatinib 320 mg/day….On day 63, selpercatinib 160 mg/day was restarted after improvement of the hepatic disorder. Since then, selpercatinib was continued without any severe adverse events. Selpercatinib is a reasonable treatment option for RET fusion-positive advanced non-small cell lung cancer even in older patients.