| Belgian International | 2019/09/12 13:00 | Luis Enrique Penalver v Leon Seiwald | L | 2-1 |
| Kharkiv Int. Qual | 2019/09/04 11:30 | Leon Seiwald v Gergo Pytel | L | 1-2 |
| Belarus Int. | 2019/08/30 10:40 | Raul Must v Leon Seiwald | L | 2-1 |
| Slovenia International - Feminin | 2019/05/15 08:30 | Leon Seiwald v B.M. Rahul Bharadwaj | L | 0-2 |
| Swiss Open - Dublu Feminin - Calificari | 2019/02/21 09:10 | Bobby Setiabudi v Leon Seiwald | L | 2-0 |
| Swiss Open - Dublu Feminin - Calificari | 2018/12/13 13:45 | Mikkel Enghoj v Leon Seiwald | W | 0-1 |
| Swiss Open - Dublu Feminin - Calificari | 2018/12/13 08:30 | Christopher Grimley v Leon Seiwald | W | 0-2 |
| Giraldilla Int. XD | 2018/11/02 09:55 | Jesper Toft v Leon Seiwald | L | 2-1 |
| Lithuanian International | 2019/06/07 11:15 | Joonas Korhonen v Jan Louda | L | 1-2 |
| Latvia Int. | 2019/05/31 14:00 | Joonas Korhonen v Richard Kuhl | W | 2-0 |
| Croatian International | 2019/04/19 08:30 | Joonas Korhonen v Martin Bundgaard | L | 0-2 |
| Finnish Open Qual | 2019/04/04 07:45 | Joonas Korhonen v Abhinav Manota | W | 2-0 |
| Swiss Open - Dublu Feminin - Calificari | 2019/03/07 10:30 | Alvaro Vazquez v Joonas Korhonen | L | 2-0 |
| Swiss Open - Dublu Feminin - Calificari | 2019/01/17 16:30 | Joonas Korhonen v Henri Hurskainen | L | 1-2 |
| Swiss Open - Dublu Feminin - Calificari | 2019/01/10 15:00 | Johnnie Torjussen v Joonas Korhonen | L | 2-0 |
| Swiss Open - Dublu Feminin - Calificari | 2019/01/10 07:00 | Joonas Korhonen v Felix Hammes | W | 2-0 |