Stadium: TVM Court (3) Round: 27 Ground: Hardcourt outdoor
| ITF M15 Troisdorf | 2021/05/13 09:00 | Mertens, Yannick v Johnson, Luke | 7-6,6-4 |
| ITF M15 Troisdorf | 2021/05/12 12:00 | Mertens, Yannick v Max Wiskandt | 7-6,6-3 |
| Sibenik, Singles M-ITF-CRO-05A | 2021/04/21 12:05 | Gergely Madarasz v Mertens, Yannick | 6-4,5-7,6-3 |
| ITF M25 Meerbusch | 2021/04/15 10:00 | Erler, Alexander v Mertens, Yannick | 6-3,3-6,6-1 |
| ITF M25 Meerbusch | 2021/04/13 13:30 | Mertens, Yannick v Vanneste, Jeroen | 6-3,6-4 |
| ITF - M15 Monastir | 2021/03/11 08:30 | Mertens, Yannick v Naoki Nakagawa | 6-4,3-6,4-6 |
| ITF - M15 Monastir | 2021/03/10 10:30 | Mertens, Yannick v Schmitz, Constantin | 6-0,6-2 |
| ITF - M15 Monastir | 2021/02/13 08:30 | Mertens, Yannick v Gauthier Onclin | 6-3,1-6,2-6 |
| ITF M15 Troisdorf | 2021/05/13 11:05 | Juan Pablo Paz v Elmar Ejupovic | 6-7,4-6 |
| ITF M15 Troisdorf | 2021/05/12 13:00 | Oscar Moraing v Elmar Ejupovic | 3-6,3-6 |
| ITF M25 Meerbusch | 2021/04/17 12:55 | Elmar Ejupovic v Erler, Alexander | 3-6,4-6 |
| ITF M25 Meerbusch | 2021/04/16 10:45 | Elmar Ejupovic v Peter Heller | 6-3,7-6 |
| ITF M25 Meerbusch | 2021/04/15 11:55 | Elmar Ejupovic v Niels Visker | 6-2,6-3 |
| ITF M25 Meerbusch | 2021/04/14 14:35 | Rudolf Molleker v Elmar Ejupovic | 6-7,6-4,3-6 |
| ITF - M25 Trimbach | 2021/03/14 09:55 | Gijs Brouwer v Elmar Ejupovic | 7-5,6-0 |
| ITF - M25 Trimbach | 2021/03/13 11:00 | Elmar Ejupovic v Matteo Martineau | 4-6,7-6,6-3 |