| UTR Pro Tennis Series Mulheim | 2021/09/22 09:30 | Buvaysar Gadamauri v Jose A R Rodriguez | 6-1,5-1 |
| UTR Pro Tennis Series Mulheim | 2021/09/21 13:00 | Buvaysar Gadamauri v Guy Den Heijer | 6-4,6-6 |
| UTR Pro Tennis Series Mulheim | 2021/09/20 12:30 | Guy Den Heijer v Lawrence Bataljin | 6-0,5-1 |
| ITF M25 Eupen | 2021/09/09 09:00 | Romain Faucon v Guy Den Heijer | 6-4,6-4 |
| ITF M25 Eupen | 2021/09/08 07:30 | Guy Den Heijer v Kai Wehnelt | 3-6,6-3,6-2 |
| 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 |