Stadium: Court 2 Round: 54 Ground: Clay
| ITF - M15 Esch/Alzette | 2021/07/18 13:30 | Andrew Fenty v Lucas Szewczyk | 1-6,5-7 |
| ITF - M15 Esch/Alzette | 2021/07/18 14:25 | Floris Podzimek v Guillaume Dermiens | 3-6,1-6 |
| ITF - M25 Marburg | 2021/07/05 08:00 | Florian Broska v Guillaume Dermiens | 7-5,6-4 |
| ITF - M25 Alkmaar | 2021/06/21 14:25 | Guillaume Dermiens v Zachary Eisinga | 4-6,7-5,13-11 |
| ITF - M25 Alkmaar | 2021/06/20 10:30 | Takanyi Garanganga v Guillaume Dermiens | 3-6,1-6 |
| ITF - M15 - Antalya | 2021/06/08 07:00 | Franco Roncadelli v Guillaume Dermiens | 6-2,6-0 |
| ITF - M15 - Antalya | 2021/06/07 09:35 | Credit Chaiyarin v Guillaume Dermiens | 0-6,4-6 |
| ITF - M15 - Antalya | 2021/05/31 08:30 | Nicolas Parizzia v Guillaume Dermiens | 6-3,1-6,10-5 |
| ITF - M15 Monastir | 2021/04/11 11:00 | Guillaume Dermiens v Arthur Bouquier | 6-4,5-7,10-12 |