Tinospora hainanensis H. S. Lo et Z. X. Li (Menispermaceae), distributed in Hainan Island, China, has stems used as an anti-inflammatory for arthritis. This study deals with the isolation and structural elucidation of compounds from its stems. From the ethanolic extract of dried stems, a new N-methyltetrahydroprotoberberine alkaloid, N-methyltetrahydrocolumbamine (1), was isolated along with five known compounds: columbamine (2), makisterone A (3), 24-epi-makisterone A (4), 20-hydroxyecdysone (5), and syringin (6). The structure of 1 was determined by FAB-MS, EI-MS, 1H-NMR, 13C-NMR (including heteronuclear multiple bond connectivity, HMBC), and single-crystal X-ray diffraction, revealing it as a 2,3,9,10-tetrasubstituted-N-methyltetrahydroprotoberberine.