| UTR Pro Tennis Series Sofia | 2021/08/31 08:00 | Christos Keisidis v Josh Sheehy | 4-6,4-6 |
| UTR Pro Tennis Series Sofia | 2021/08/30 07:00 | Christos Keisidis v Denislav Prodanov | 6-1,5-1 |
| ITF M15 Heraklion | 2021/06/09 08:00 | Antonio Cayetano March v Christos Keisidis | 4-6,7-6,6-2 |
| ITF M15 Heraklion | 2021/06/08 06:30 | Sean Hodkin v Christos Keisidis | 6-4,5-7,4-10 |
| ITF M15 Heraklion | 2021/06/07 09:00 | Christos Keisidis v Alexander Gaponenko | 6-4,6-1 |
| ITF M15 Heraklion | 2021/06/06 11:00 | Michel-Alexandre Fortin v Christos Keisidis | 0-6,0-6 |
| ITF M15 Heraklion | 2021/05/31 06:30 | Mattia Bellucci v Christos Keisidis | 6-4,6-3 |
| ITF M15 Heraklion | 2021/05/24 06:30 | Christos Keisidis v William Griffith | 2-6,3-6 |
| UTR Pro Tennis Series Sofia | 2021/08/31 08:00 | Denislav Prodanov v Mario Radev | 6-1,1-6,6-3 |
| UTR Pro Tennis Series Sofia | 2021/08/30 10:45 | Mario Radev v Josh Sheehy | 1-6,2-6 |
| UTR Pro Tennis Series Sofia | 2021/08/29 12:00 | George Lazarov v Mario Radev | 6-0,6-1 |