Stadium: Sparkassen Court Round: 27 Ground: Clay
| ITF M25 Marburg | 2021/07/08 09:00 | Ryan Nijboer v Tim Handel | 6-3,6-4 |
| ITF M25 Marburg | 2021/07/07 09:00 | Yan Sabanin v Ryan Nijboer | 0-6,3-6 |
| ITF M25 The Hague | 2021/06/30 12:55 | Mateus Alves v Ryan Nijboer | 7-6,6-3 |
| ITF M25 Alkmaar | 2021/06/24 12:00 | Marko Tepavac v Ryan Nijboer | 4-6,7-6,6-1 |
| ITF M15 Skopje | 2021/06/10 11:30 | Miljan Zekic v Ryan Nijboer | 6-2,6-3 |
| ITF M15 Skopje | 2021/06/10 07:45 | Ryan Nijboer v Dian Nedev | 6-3,6-2 |
| ITF M15 Skopje | 2021/06/06 07:55 | Alexis Gautier v Ryan Nijboer | 6-2,3-6,6-2 |
| ITF M15 Skopje | 2021/06/05 10:40 | Dalibor Svrcina v Ryan Nijboer | 6-1,4-6,5-7 |
| ITF M25 Marburg | 2021/07/08 08:55 | Milan Welte v Neo Niedner | 6-2,6-1 |
| ITF M25 Marburg | 2021/07/07 12:30 | Daniel Cukierman v Milan Welte | 4-6,4-6 |
| ITF M25 Marburg | 2021/07/06 15:00 | Milan Welte v Raphael Collignon | 7-6,6-3 |
| ITF M25 Marburg | 2021/07/05 13:05 | Milan Welte v Christopher Patzanovsky | 6-1,6-3 |
| ITF M15 Heraklion | 2021/05/17 07:00 | Milan Welte v Tom Gentzsch | 6-0,6-3 |
| ITF M15 Troisdorf | 2021/05/09 13:00 | Yannik Steinegger v Milan Welte | 6-4,6-2 |
| ITF M25 Meerbusch | 2021/04/16 09:00 | Milan Welte v Alexander Erler | 1-6,4-6 |
| ITF M25 Meerbusch | 2021/04/15 10:00 | Markus Eriksson v Milan Welte | 3-6,1-6 |