Stadium: Court 1 Round: 26 Ground: Clay
| ITF M15 Antalya | 2021/04/26 07:00 | Fabrizio Andaloro v Simeon Terziev | 4-6,6-4,11-9 |
| ITF M15 Antalya | 2021/04/25 07:00 | Credit Chaiyarin v Simeon Terziev | 3-6,1-6 |
| ITF M15 Antalya | 2021/04/18 07:00 | Kristof Minarik v Simeon Terziev | 6-1,6-1 |
| UTR Pro Tennis Series Pazardzhik | 2021/04/03 10:00 | Jules Marie v Simeon Terziev | 6-3,6-0 |
| UTR Pro Tennis Series Pazardzhik | 2021/04/02 07:00 | Ilya Snitari v Simeon Terziev | 6-0,6-3 |
| UTR Pro Tennis Series Pazardzhik | 2021/04/01 07:00 | Yurii Dzhavakian v Simeon Terziev | 4-6,4-5 |
| UTR Pro Tennis Series Pazardzhik | 2021/03/29 09:00 | Simeon Terziev v Gergely Madarasz | 3-6,1-6 |
| ITF M15 Antalya | 2021/03/08 10:00 | Stefan Palosi v Simeon Terziev | 6-3,6-0 |
| ITF M15 Cairo | 2021/05/04 09:45 | Gabriel Donev v Benedikt Emesz | 6-2,6-2 |
| ITF M15 Cairo | 2021/05/03 08:00 | Gabriel Donev v Santiago De La Fuente | 7-5,1-6,17-15 |
| ITF M15 Cairo | 2021/04/28 09:35 | Carlos Sanchez Jover v Gabriel Donev | 6-1,6-2 |
| UTR Pro Tennis Series Pazardzhik | 2021/04/10 10:30 | Gergely Madarasz v Gabriel Donev | 4-6,6-3,6-0 |
| UTR Pro Tennis Series Pazardzhik | 2021/04/09 11:30 | Gabriel Donev v Ronan Joncour | 5-7,3-6 |
| UTR Pro Tennis Series Pazardzhik | 2021/04/07 09:30 | Gabriel Donev v Plamen Milushev | 7-5,6-3 |
| UTR Pro Tennis Series Pazardzhik | 2021/04/06 08:30 | Gabriel Donev v Yanaki Milev | 6-2,5-1 |
| UTR Pro Tennis Series Pazardzhik | 2021/04/05 13:00 | Constant De La Bassetiere v Gabriel Donev | 5-7,1-6 |