Stadium: TSITSIPAS COURT Round: 26 Ground: Hardcourt outdoor
| ITF M25 Alkmaar | 2021/06/20 17:00 | Alec Deckers v Guy Den Heijer | 3-6,7-6,4-10 |
| ITF M15 Heraklion | 2021/11/10 07:00 | Guy Den Heijer v Max Houkes | 7-6,6-3 |
| UTR Pro Tennis Series Amsterdam | 2021/11/07 10:30 | Guy Den Heijer v Sem Verbeek | 6-3,6-3 |
| UTR Pro Tennis Series Amsterdam | 2021/11/06 12:00 | Deney Wassermann v Guy Den Heijer | 2-6,5-6 |
| UTR Pro Tennis Series Amsterdam | 2021/11/05 13:30 | Guy Den Heijer v Johann Willems | 7-6,2-6,6-4 |
| UTR Pro Tennis Series Amsterdam | 2021/11/03 10:30 | Guy Den Heijer v Lawrence Bataljin | 6-0,6-3 |
| UTR Pro Tennis Series Amsterdam | 2021/11/02 10:30 | Guy Den Heijer v Jip Van Assendelft | 6-4,5-2 |
| UTR Pro Tennis Series Amsterdam | 2021/11/01 13:30 | Miko Wassermann v Guy Den Heijer | 2-6,5-7 |
| ITF M15 Girona | 2021/10/19 08:00 | Guy Den Heijer v Vladislav Ivanov | 6-4,6-3 |
| ITF M15 Heraklion | 2021/11/10 10:00 | Zsombor Velcz v Alec Deckers | 6-3,0-6,4-6 |
| ITF M15 Heraklion | 2021/11/09 07:00 | Alec Deckers v Stephanos Schinas | 6-0,7-5 |
| ITF M15 Heraklion | 2021/11/08 08:00 | Alec Deckers v Gosse Panagoulopoulos | 6-1,6-3 |
| ITF M15 Heraklion | 2021/11/07 07:00 | Alec Deckers v Ioannis Papounidis | 6-3,7-5 |
| ITF M15 Doha | 2021/10/20 14:15 | Niklas Schell v Alec Deckers | 6-4,6-2 |
| ITF M15 Doha | 2021/10/17 13:30 | Alec Deckers v Valentin Vacherot | 6-4,3-6,6-3 |
| ITF M15 Doha | 2021/10/16 13:00 | Alec Deckers v Oscar Moraing | 7-5,6-3 |
| ITF M15 Doha | 2021/10/15 13:00 | Daniel Cox v Alec Deckers | 4-6,6-3,6-7 |