Stadium: COURT 1 Round: 25 Ground: Clay
| ITF M15 Lodz | 2021/08/19 10:30 | Daniel Michalski v Szymon Kielan | 3-6,7-5,6-3 |
| ITF M15 Lodz | 2021/08/18 09:30 | Roman Andres Burruchaga v Szymon Kielan | 6-7,3-6 |
| ITF M15 Gdynia | 2021/08/12 10:25 | Szymon Kielan v Alexis Musialek | 3-6,4-6 |
| ITF M15 Gdynia | 2021/08/11 14:25 | Luke Johnson v Szymon Kielan | 1-6,6-7 |
| ITF M25 Grodzisk Mazowiecki | 2021/08/04 17:10 | David Poljak v Szymon Kielan | 7-5,6-3 |
| Polish National Tour | 2021/07/11 10:00 | Kamil Majchrzak v Szymon Kielan | 6-1,7-6 |
| ITF M25 Wroclaw | 2021/06/30 13:15 | Gonzalo Lama v Szymon Kielan | 6-1,6-2 |
| ITF M25 Wroclaw | 2021/06/29 08:00 | Szymon Kielan v Mateusz Terczynski | 6-3,6-2 |
| Challenger Verona | 2021/08/17 12:10 | Goncalo Oliveira v Paolo Lorenzi | 3-6,3-6 |
| Challenger Prague | 2021/08/11 09:50 | Goncalo Oliveira v Dmitry Popko | 0-6,3-6 |
| Challenger Prague | 2021/08/10 09:30 | Toby Alex Kodat v Goncalo Oliveira | 3-6,1-6 |
| Challenger Segovia | 2021/07/27 09:30 | Alejandro Moro Canas v Goncalo Oliveira | 3-6,7-6,6-1 |
| Challenger Amersfoort | 2021/07/13 10:00 | Goncalo Oliveira v Botic Van De Zandschulp | 2-6,4-6 |
| Challenger Porto | 2021/07/02 12:00 | Goncalo Oliveira v Sergiy Stakhovsky | 6-7,6-7 |
| Challenger Porto | 2021/06/30 10:00 | Peter Polansky v Goncalo Oliveira | 6-7,4-6 |
| Challenger Porto | 2021/06/29 10:00 | Goncalo Oliveira v Nuno Borges | 6-1,6-2 |