Stadium: Court 4 Round: 54 Ground: Clay
| ITF - M25 Alkmaar | 2021/06/23 09:00 | Kaichi Uchida v Guy Den Heijer | 7-6,6-3 |
| ITF - M25 Alkmaar | 2021/06/21 18:00 | Vladimir Ivanov v Guy Den Heijer | 3-6,6-7 |
| ITF - M25 Alkmaar | 2021/06/20 17:00 | Alec Deckers v Guy Den Heijer | 3-6,7-6,4-10 |
| ITF - M25 Vic | 2021/05/16 08:00 | Mateus Alves v Guy Den Heijer | 6-2,6-3 |
| ITF - M15 Valldoreix | 2021/05/09 13:00 | Guy Den Heijer v Pol Amoros Ramos | 3-6,2-6 |
| ITF - M15 Majadahonda | 2021/05/02 16:15 | Taiyo Yamanaka v Guy Den Heijer | 6-7,6-3,11-9 |
| ITF - M15 Antalya | 2021/03/25 07:00 | Guy Den Heijer v Juan Pablo Paz | 1-6,2-6 |
| ITF - M15 Antalya | 2021/03/24 06:30 | Guy Den Heijer v Carlo Alberto Fossati | 6-2,6-3 |
| ITF - M15 Antalya | 2021/05/09 07:00 | Jing L Weng v Mark Tryakshin | 2-6,5-7 |
| ITF - M15 Antalya | 2021/05/02 06:00 | Vladislav Melnic v Jing L Weng | 6-4,6-0 |
| ITF - M25 Meerbusch | 2021/04/12 09:30 | David Pichler v Jing L Weng | 6-2,6-1 |
| ITF - M25 Meerbusch | 2021/04/11 12:45 | Jing L Weng v Amer Naow | 6-4,7-5 |
| ITF - M15 Sharm El Sheikh | 2021/03/10 11:20 | Jing L Weng v Lukas Krainer | 2-6,1-6 |
| ITF - M15 Sharm El Sheikh | 2021/02/28 11:00 | Jing L Weng v Lukas Krainer | 0-6,3-6 |
| ITF - M15 Sharm El Sheikh | 2021/02/21 09:30 | Chien Hsun Lo v Jing L Weng | 6-1,7-5 |
| ITF - M15 Alkmaar | 2020/08/23 08:30 | Jing L Weng v Raphael Collignon | 0-6,2-6 |