| ITF M25 Hamburg | 2021/10/17 07:55 | Tom Schonenberg v Kai Lemstra | 6-2,6-2 |
| ITF M15 Heraklion | 2021/11/23 07:00 | Nicholas David Ionel v Kai Lemstra | 3-6,7-5,10-4 |
| ITF M15 Heraklion | 2021/11/22 08:00 | Sergis Kyratzis v Kai Lemstra | 4-6,2-6 |
| ITF M15 Heraklion | 2021/11/21 07:00 | Liam Puttergill v Kai Lemstra | 2-6,1-6 |
| ITF M15 Heraklion | 2021/11/17 08:05 | Alastair Gray v Kai Lemstra | 6-1,7-5 |
| ITF M15 Heraklion | 2021/11/16 07:00 | Max Houkes v Kai Lemstra | 4-6,6-7 |
| ITF M15 Heraklion | 2021/11/15 08:00 | Alan Gleeson v Kai Lemstra | 6-7,3-6 |
| ITF M15 Heraklion | 2021/11/12 10:05 | Kai Lemstra v Peter Fajta | 6-4,1-6,2-6 |
| ITF M15 Heraklion | 2021/11/11 07:00 | Tim Handel v Kai Lemstra | 3-6,6-7 |
| German Championship | 2021/12/06 10:30 | Tom Schonenberg v Philipp Mayer | 6-3,6-2 |
| German Championship | 2021/12/05 10:30 | Tom Schonenberg v Andre Steinbach | 7-5,6-4 |
| ITF M25 Villers Les Nancy | 2021/11/09 10:40 | Antoine Escoffier v Tom Schonenberg | 6-3,6-3 |
| ITF M25 Villers Les Nancy | 2021/11/08 09:00 | Raphael Calzi v Tom Schonenberg | 6-4,2-6,7-10 |
| ITF M25 Villers Les Nancy | 2021/11/07 13:30 | Tom Biston v Tom Schonenberg | 1-6,2-6 |
| ITF M25 Sarreguemines | 2021/10/25 12:00 | Hendrik Jebens v Tom Schonenberg | 7-6,6-4 |
| ITF M25 Sarreguemines | 2021/10/24 14:00 | Antoine Vincent v Tom Schonenberg | 3-6,4-6 |
| ITF M25 Hamburg | 2021/10/19 10:55 | Tom Schonenberg v Vladyslav Orlov | 3-6,6-7 |