Stadium: Court 7 Round: 26 Ground: Hardcourt outdoor
| ITF M15 Sozopol | 2021/10/13 14:00 | Tsivadze, George v Terziev, Simeon | 2-6,0-2 |
| ITF M15 Sozopol | 2021/10/05 10:00 | Terziev, Simeon v Billy Harris | 1-6,5-7 |
| ITF M15 Sozopol | 2021/09/16 08:00 | Valentin Vacherot v Terziev, Simeon | 6-0,6-3 |
| ITF M15 Sozopol | 2021/09/14 10:00 | Terziev, Simeon v Dinko Dinev | 6-4,6-2 |
| UTR Pro Tennis Series Sofia | 2021/09/02 10:00 | Terziev, Simeon v Dzhavakian, Yurii | 3-6,7-6,3-6 |
| UTR Pro Tennis Series Sofia | 2021/09/01 06:30 | Terziev, Simeon v Adriano Dzhenev | 6-1,6-2 |
| UTR Pro Tennis Series Sofia | 2021/08/31 11:00 | Terziev, Simeon v Veselin Kiselkov | 6-1,5-0 |
| UTR Pro Tennis Series Sofia | 2021/08/30 10:00 | Ioan Alexandru Chirita v Terziev, Simeon | 4-6,6-3,3-6 |
| ITF M15 Sozopol | 2021/10/13 09:00 | Dragomir Draganov v Alexander Donski | 1-6,2-6 |
| ITF M15 Sozopol | 2021/10/09 07:00 | Alexander Donski v Kai Wehnelt | 6-4,3-6,6-7 |
| ITF M15 Sozopol | 2021/10/08 08:35 | Tim Handel v Alexander Donski | 3-6,6-3,2-6 |
| ITF M15 Sozopol | 2021/10/05 15:15 | Ignat, Dragos Constantin v Alexander Donski | 1-6,2-6 |
| Sofia, Bulgaria | 2021/09/27 09:00 | Seppi, Andreas v Alexander Donski | 6-3,6-2 |
| Sofia, Bulgaria | 2021/09/26 09:00 | Alexander Donski v Jurij Rodionov | 2-6,6-1,7-6 |
| ITF M25 Plaisir | 2021/09/16 09:55 | Robin Bertrand v Alexander Donski | 3-6,3-6 |
| ITF M25 Plaisir | 2021/09/14 08:00 | Alexander Donski v Robert, Quentin | 7-5,1-6,6-2 |