Stadium: Center Court Round: 45 Ground: Carpet indoor
| Challenger Eckental Qual | 2017/10/30 11:20 | Kern, Robin v Sieber, Marc | 6-4,6-2 |
| Challenger Ortisei | 2018/10/06 12:05 | Lenz, Julian v Kern, Robin | 6-3,6-2 |
| Orleans, France | 2018/09/22 15:15 | Hugo Grenier v Kern, Robin | 6-1,6-1 |
| ITF Italy F25 | 2018/08/30 12:30 | Reinwein, Sami v Kern, Robin | 7-6,6-4 |
| ITF Italy F25 | 2018/08/29 12:00 | Gabriele Maria Noce v Kern, Robin | 3-6,3-6 |
| ITF Italy F25 | 2018/08/28 17:00 | Pasquale De Giorgio v Kern, Robin | 4-6,3-6 |
| ITF Portugal F16 | 2018/08/22 09:00 | Nicolas Alvarez Varona v Kern, Robin | 6-2,6-2 |
| ITF Germany F12 | 2018/08/16 13:10 | Aleksandre Metreveli v Kern, Robin | 7-5,7-5 |
| ITF Germany F12 | 2018/08/14 15:00 | Moritz Hoffmann v Kern, Robin | 2-6,3-6 |
| Challenger Ortisei | 2018/10/06 13:30 | Sieber, Marc v Albano Olivetti | 6-4,6-7,4-6 |
| ITF Germany F14 | 2018/10/04 15:05 | Francesco Ferrari v Sieber, Marc | 2-6,6-4,6-3 |
| ITF Germany F14 | 2018/10/02 10:00 | Max Wiskandt v Sieber, Marc | 2-6,0-6 |
| ITF Germany F14 | 2018/10/01 10:00 | Sieber, Marc v von Der Schulenburg, Henry | 6-1,6-2 |
| ITF Germany F14 | 2018/09/30 11:30 | Sieber, Marc v Nystroem, Patrick | 6-1,7-5 |
| Challenger Sibiu Qual | 2018/09/16 12:00 | Frunza, Nicolae v Sieber, Marc | 6-4,6-3 |
| Challenger Seville | 2018/09/01 16:00 | Sieber, Marc v Bernabe Zapata Miralles | 6-7,3-6 |
| Challenger Mallorca | 2018/08/26 11:30 | Federico Zeballos v Sieber, Marc | 3-6,6-1,6-3 |