Known as Masaaki Uchino (内野 聖陽 Uchino Masaaki) until July 2013, when he changed the pronunciation (though not the spelling) of his stage name to Seiyo Uchino (内野 聖陽 Uchino Seiyō).
| Series | Pararescue Jumper | Seiji Usami | 2025-04-24 |
| Series | Asura | Sadaharu Masukawa | 2025-01-09 |
| Movie | Hakkenden | Hokusai Katsushika | 2024-10-01 |
| Movie | Angry Squad: Civil Servants & Seven Swindlers | Jiro Kumazawa | 2024-11-22 |
| Movie | Picture of Spring | Ichirou Haga | 2023-10-13 |
| Movie | Fullmetal Alchemist: The Final Alchemy | Van Hohenheim / "Father"/ The Dwarf in the Flask (voice) | 2022-06-24 |
| Movie | Fullmetal Alchemist: The Revenge of Scar | Van Hohenheim / "Father" | 2022-05-20 |
| Movie | Homunculus | Kumicho | 2021-04-02 |
| Series | Welcome Home, Mone | Nagaura Koji | 2021-05-17 |
| Movie | What Did You Eat Yesterday? New Year's Special 2020 | Kenji Yabuki | 2020-01-01 |
| Series | Bones of Steel | 2020-04-18 | |
| Movie | A Samurai Movie Rhapsody: Filming the Ultimate Swordfight | 2019-03-23 | |
| Movie | First Love | Gondō | 2019-05-31 |
| Series | What Did You Eat Yesterday? | Kenji Yabuki | 2019-04-06 |
| Series | Black Pean | Seigo Saeki | 2018-04-22 |
| Movie | Kohaku no yume | 2018-10-05 | |
| Movie | Premium Stage "Hamlet" | 2017-07-02 | |
| Movie | Room Leader | Nobuhiko Kamamoto | 2017-12-17 |
| Movie | The Driver | Joichiro Konoe | 2015-10-11 |
| Movie | 125 Years Memory | Motosada Tamura | 2015-12-05 |
| Movie | Crime's Blank | Ando | 2015-10-23 |
| Series | Leaders | 2014-03-22 | |
| Movie | Homeland | Souichi | 2014-03-01 |
| Movie | Jikan no Shûzoku | Kiichi Mihara | 2014-04-10 |
| Series | Back of Father | 2014-07-13 | |
| Series | Black Kite | Yasuo Ichikawa | 2013-01-13 |
| Movie | Lupin the Third vs. Detective Conan: The Movie | Alan Smithee (voice) | 2013-12-07 |
| Series | Onna Nobunaga | 2013-04-05 | |
| Movie | Chuushingura Sono Gi Sono Ai | Horibe Yasube | 2012-01-02 |
| Movie | The Last Message | Yoshio Kuraishi | 2012-06-30 |
| Movie | Happy Together –All About My Dog– | Detective Watanabe | 2011-01-22 |
| Series | The History of Our Family | Kozo Masuda | 2010-04-09 |
| Series | I'll Still Love You in 10 Years | Hiroshi Maruyama | 2010-08-31 |
| Movie | 13 Assassins | Zusho Mamiya | 2010-09-25 |
| Series | Rinjo | Yoshio Kuraishi | 2009-04-15 |
| Movie | Elevator Trap | 2009-10-10 | |
| Movie | The Wonderful World of Captain Kuhio | Fujiwara | 2009-10-10 |
| Series | Jin | Ryoma Sakamoto | 2009-10-11 |
| Series | Gonzo: The Legendary Detective | Kuroki | 2008-07-02 |
| Movie | 252: Signal of Life | Shizuma Shinohara | 2008-12-06 |
| Movie | The Road to Sirius | Yusuke Tatsumura | 2008-09-14 |
| Series | Samurai Banners | 2007-01-07 | |
| Movie | Akanezora Beyond the Crimson Sky | Eikichi / Denzo | 2007-03-31 |
| Series | Fukigen na Gene | Minamihara Takashi | 2005-01-17 |
| Series | Aim for the Ace! | Munakata Jin | 2004-01-15 |
| Movie | People Without a Fort | Kurashina Kenji | 2004-09-24 |
| Movie | The Black House | Shinji Wakatsuki | 1999-11-13 |
| Series | Love Generation | Soichiro Katagiri | 1997-10-13 |
| Movie | Haru | Noboru Hayami 'Haru' | 1996-03-09 |
| Movie | A Last Note | Koji Kiyokawa | 1995-06-03 |