| UTR Pro Copenhagen | 2023/02/15 07:00 | Igor Skoric v Hugo Pierre | 2-6,1-6 |
| UTR Pro Copenhagen | 2023/02/15 07:00 | Wadym Konowczuk v Jakub Ostajewski | 4-6,1-6 |
| UTR Pro Copenhagen | 2023/02/13 12:45 | Ivan Sodan v Jakub Ostajewski | 6-3,7-6 |
| ITF M15 Palm Coast | 2023/02/06 16:30 | Jakub Ostajewski v Benjamin Denis Alarcon | 4-6,3-6 |
| ITF M25 Wesley Chapel | 2023/01/23 14:45 | Thomas Brown v Jakub Ostajewski | 6-3,6-1 |
| ITF M25 Malibu | 2023/01/02 17:00 | Alex Kuperstein v Jakub Ostajewski | 7-6,6-2 |
| ITF M15 Boca Raton | 2022/11/14 16:00 | Sean Daryabeigi v Jakub Ostajewski | 6-2,6-3 |
| ITF M15 Winston-Salem | 2022/11/07 18:00 | James Story v Jakub Ostajewski | 6-2,7-5 |
| ITF M15 Lubbock | 2022/09/21 17:05 | Jakub Ostajewski v Jakub Wojcik | 4-6,4-6 |