Stadium: TSITSIPAS COURT Round: 62 Ground: Hardcourt outdoor
| ITF M15 Selva Gardena | 2021/10/27 08:00 | Kai Lemstra v Mattia Bellucci | 3-6,3-6 |
| ITF M15 Selva Gardena | 2021/10/26 07:30 | Kai Lemstra v Carlo Alberto Fossati | 6-4,7-5 |
| ITF M15 Selva Gardena | 2021/10/25 08:30 | Kai Lemstra v Dominique Graf | 7-5,6-2 |
| ITF M15 Selva Gardena | 2021/10/24 10:45 | Kai Lemstra v Davide Ferrarolli | 6-4,6-3 |
| ITF M25 Hamburg | 2021/10/17 07:55 | Tom Schonenberg v Kai Lemstra | 6-2,6-2 |
| ITF M15 Monastir | 2021/08/26 07:30 | Kai Lemstra v Renta Tokuda | 2-6,2-6 |
| ITF M15 Monastir | 2021/08/25 07:30 | Hamzeh Al-Aswad v Kai Lemstra | 2-6,1-6 |
| ITF M15 Monastir | 2021/08/24 07:30 | Seita Watanabe v Kai Lemstra | 1-6,1-6 |
| ITF M15 Heraklion | 2021/11/01 11:00 | Drew Van Orderlain v Christian Fellin | 6-3,2-6,6-10 |
| UTR Pro Tennis Series Copenhagen | 2021/10/24 08:30 | Henrik Heise Korsgaard v Drew Van Orderlain | 3-6,7-6,6-2 |
| UTR Pro Tennis Series Copenhagen | 2021/10/20 10:00 | Drew Van Orderlain v Alexander Stage | 6-4,3-6,6-3 |
| UTR Pro Tennis Series Copenhagen | 2021/10/19 08:30 | Drew Van Orderlain v Marius Ruzgas | 3-6,4-6 |
| UTR Pro Tennis Series Copenhagen | 2021/10/18 08:30 | Drew Van Orderlain v Adam Heinonen | 4-6,5-7 |
| UTR Pro Tennis Series Atlanta | 2021/04/16 17:00 | Drew Van Orderlain v Ronan Jachuck | 3-6,3-6 |
| UTR Pro Tennis Series Atlanta | 2021/04/15 16:30 | Drew Van Orderlain v Matthias Haim | 5-7,3-6 |
| UTR Pro Tennis Series Atlanta | 2021/04/14 16:30 | Evan Bynoe v Drew Van Orderlain | 6-4,6-1 |