Stadium: Centre Court Round: 25 Ground: Clay
| ITF Austria F3 | 2017/07/18 10:20 | Peter Heller v Kai Lemstra | 4-6,6-3,6-3 |
| Challenger - Augsburg | 2019/08/06 12:55 | Peter Heller v Vilella Martinez, Mario | 2-6,2-6 |
| Challenger - Augsburg | 2019/08/05 10:55 | Oriol Roca Batalla v Peter Heller | 5-7,7-6,4-6 |
| Challenger Liberec | 2019/07/29 10:25 | Geoffrey Blancaneaux v Peter Heller | 6-3,6-3 |
| Challenger - Prague | 2019/07/25 09:30 | Chun Hsin Tseng v Peter Heller | 6-7,6-3,6-3 |
| Challenger - Prague | 2019/07/24 08:00 | Peter Heller v Ignatik, Uladzimir | 6-1,6-4 |
| Challenger - Prague | 2019/07/23 08:00 | Peter Heller v Vit Kopriva | 6-2,6-3 |
| Braunchsweig, Germany | 2019/07/07 08:00 | Carlos Taberner v Peter Heller | 7-6,6-1 |
| Ludwigshafen, Allemagne | 2019/07/03 09:00 | Daniel Elahi Galan v Peter Heller | 6-3,7-6 |
| ITF M15 Trier | 2019/08/13 11:05 | Kai Lemstra v Walder, Jordi | 4-6,2-6 |
| Challenger - Augsburg | 2019/08/05 12:25 | Facundo Mena v Kai Lemstra | 6-4,6-2 |
| Bad Schussenried, Singles Qualifying M-ITF-GER-10A | 2019/07/23 14:35 | Nik Razborsek v Kai Lemstra | 6-2,6-3 |
| Bad Schussenried, Singles Qualifying M-ITF-GER-10A | 2019/07/22 13:00 | de Valk, Roy Sarut v Kai Lemstra | 5-7,4-6 |
| Bad Schussenried, Singles Qualifying M-ITF-GER-10A | 2019/07/22 08:00 | Kunz, Giordan v Kai Lemstra | 1-6,1-6 |
| Kramsach, Singles M-ITF-AUT-02A | 2019/07/17 09:00 | Kai Lemstra v van Den Berg, Bart | 4-6,2-6 |
| Kramsach, Singles M-ITF-AUT-02A | 2019/07/15 13:30 | Kai Lemstra v Holis, Evzen | 6-3,4-6,10-6 |
| ITF M15 Troisdorf | 2019/05/06 14:00 | Veldheer, Mick v Kai Lemstra | 2-6,6-1,10-7 |