Stadium: Swiss Post Court Round: 25 Ground: Clay
| ITF M25 Eupen | 2021/09/07 10:05 | Guy Den Heijer v Tom Gentzsch | 6-3,6-4 |
| ITF M25 Eupen | 2021/09/06 14:45 | Guy Den Heijer v Yannick Lenaerts | 6-1,6-0 |
| ITF M15 Oldenzaal | 2021/08/21 10:10 | Guy Den Heijer v Damien Wenger | 4-6,2-6 |
| ITF M15 Oldenzaal | 2021/08/20 16:35 | Guy Den Heijer v Alexander Hoogmartens | 6-3,6-7,6-4 |
| ITF M15 Oldenzaal | 2021/08/20 10:20 | Sander Jong v Guy Den Heijer | 5-7,7-5,4-6 |
| ITF M15 Oldenzaal | 2021/08/18 12:35 | Vladimir Ivanov v Guy Den Heijer | 6-4,4-6,4-6 |
| ITF M15 Oldenzaal | 2021/08/17 09:15 | Guy Den Heijer v Alexis Canter | 6-4,6-4 |
| ITF M15 Oldenzaal | 2021/08/16 10:00 | Guy Den Heijer v Noel Larwig | 6-3,6-4 |
| ITF M25 Trier | 2021/08/26 11:00 | Quentin Folliot v Kai Wehnelt | 7-5,4-6,7-5 |
| ITF M25 Trier | 2021/08/24 13:30 | Kai Wehnelt v Sarp Agabigun | 6-0,6-4 |
| ITF M15 Oldenzaal | 2021/08/18 14:30 | Kai Wehnelt v Daniel De Jonge | 5-7,6-1,6-7 |
| ITF M25 Frankfurt am Main | 2021/08/11 15:30 | Kai Wehnelt v Lucas Gerch | 6-3,2-6,4-6 |
| ITF M25 Wetzlar | 2021/08/04 08:00 | Harold Mayot v Kai Wehnelt | 6-4,6-7,7-5 |
| ITF M15 Cairo | 2021/07/29 08:00 | Gustavo Heide v Kai Wehnelt | 3-6,7-5,6-3 |
| ITF M15 Cairo | 2021/07/28 14:20 | Facundo Arias Bisso v Kai Wehnelt | 5-7,5-7 |
| ITF M15 Cairo | 2021/07/24 08:00 | Mathieu Perchicot v Kai Wehnelt | 6-3,1-6,7-5 |