Stadium: Hard 21 Round: 26 Ground: Hardcourt outdoor
| ITF Germany F7 | 2018/07/09 08:00 | Kai Lemstra v Tim Handel | 4-6,7-5,6-1 |
| 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 | Tim Handel v Dominik Recek | 2-6,6-4,6-4 |
| ITF M25 Marburg | 2021/07/06 14:40 | Aleksandre Bakshi v Tim Handel | 3-6,2-6 |
| ITF M25 Marburg | 2021/07/05 14:10 | Deney Wassermann v Tim Handel | 6-7,6-7 |
| ITF M25 Klosters | 2021/06/24 11:15 | Jakub Paul v Tim Handel | 6-3,6-3 |
| ITF M25 Klosters | 2021/06/23 10:30 | Luca Castelnuovo v Tim Handel | 6-7,2-6 |
| ITF M25 Klosters | 2021/06/21 08:35 | Louroi Martinez v Tim Handel | 7-5,6-7,11-9 |
| ITF M25 Klosters | 2021/06/20 10:10 | Adrien Burdet v Tim Handel | 2-6,5-7 |
| ITF M25 Most | 2021/05/26 10:15 | Antoine Escoffier v Kai Lemstra | 6-3,7-5 |
| ITF M25 Most | 2021/05/25 10:15 | Kai Lemstra v Edward Hubner | 6-1,6-1 |
| ITF M25 Most | 2021/05/24 08:00 | Kai Lemstra v Niklas Rohrer | 6-3,6-2 |
| ITF M25 Most | 2021/05/23 14:00 | Kai Lemstra v Vojtech Petr | 6-4,6-4 |
| ITF M25 Jablonec Nad Nisou | 2021/05/18 07:30 | Andrew Paulson v Kai Lemstra | 6-3,6-4 |
| ITF M25 Jablonec Nad Nisou | 2021/05/17 07:30 | Jan Jermar v Kai Lemstra | 4-6,4-6 |
| ITF M25 Jablonec Nad Nisou | 2021/05/16 08:30 | Matyas Cerny v Kai Lemstra | 3-6,3-6 |
| ITF M25 Meerbusch | 2021/04/12 09:30 | Marvin Netuschil v Kai Lemstra | 6-2,6-3 |