Stadium: Center Court Round: 27 Ground: Clay
| ITF M25 Wetzlar | 2021/08/05 13:55 | Dayne Kelly v Constantin Schmitz | 2-6,1-6 |
| ITF M25 Wetzlar | 2021/08/04 12:30 | Constantin Schmitz v Jannik Rother | 6-2,6-0 |
| ITF M15 Troisdorf | 2021/05/12 09:00 | Constantin Schmitz v Tom Kocevar-Desman | 6-4,4-6,3-6 |
| ITF M15 Antalya | 2021/04/14 10:30 | Ivan Sergeyev v Constantin Schmitz | 6-3,5-7,6-3 |
| ITF M15 Antalya | 2021/04/08 06:55 | Flavio Cobolli v Constantin Schmitz | 7-6,7-6 |
| ITF M15 Antalya | 2021/04/06 07:00 | Constantin Schmitz v Bogdan Bobrov | 6-1,6-4 |
| ITF M15 Antalya | 2021/03/30 08:30 | Pol Martin Tiffon v Constantin Schmitz | 6-4,7-6 |
| ITF M15 Antalya | 2021/03/26 07:00 | Georgii Kravchenko v Constantin Schmitz | 6-2,6-3 |
| ITF M25 Wetzlar | 2021/08/05 09:00 | Georgii Kravchenko v Peter Heller | 6-7,2-6 |
| ITF M25 Wetzlar | 2021/08/04 08:00 | Marvin Moeller v Peter Heller | 2-6,3-6 |
| Challenger Salzburg | 2021/07/08 10:30 | Nicolas Jarry v Peter Heller | 6-2,6-4 |
| Challenger Salzburg | 2021/07/05 10:35 | Francisco Cerundolo v Peter Heller | 3-6,6-3,3-6 |
| ITF M15 Antalya | 2021/05/06 08:10 | Nick Hardt v Peter Heller | 3-6,6-0,7-5 |
| ITF M15 Antalya | 2021/05/05 08:55 | Karl Friberg v Peter Heller | 3-6,3-6 |
| ITF M15 Antalya | 2021/05/01 07:30 | Peter Heller v Jeroen Vanneste | 3-6,3-6 |
| ITF M15 Antalya | 2021/04/30 09:50 | Rio Noguchi v Peter Heller | 6-2,3-6,2-6 |