Stadium: Court 1 Round: 25 Ground: Clay
| ITF Germany F12 | 2018/08/14 11:00 | Mertens, Nico v Vilaro, Alejo | 4-6,3-6 |
| ITF Belgium F7 Qual | 2018/08/06 09:00 | Mertens, Nico v Damiens, Antoine | 6-7,4-6 |
| ITF Belgium F7 Qual | 2018/08/05 08:00 | Mertens, Nico v Leiva Biason, Oscar Mattias | 6-1,6-0 |
| ITF Germany F10 | 2018/08/01 14:05 | Mertens, Nico v Facundo Mena | 2-6,2-6 |
| ITF Germany F10 Qual | 2018/07/30 12:00 | Mertens, Nico v Nery Junior, Osni | 4-6,5-7 |
| ITF Germany F10 Qual | 2018/07/29 15:30 | Mertens, Nico v Koch, Niklas | 6-4,7-6 |
| ITF Germany F9 | 2018/07/24 10:00 | Mertens, Nico v Manuel Guinard | 0-6,6-4,4-6 |
| ITF Bosnia and Herzegovina F3 | 2018/05/29 10:40 | Mertens, Nico v Nerman Fatic | 4-6,3-6 |
| Meerbusch, Allemagne, Qualifications | 2018/08/11 14:35 | Nicola Kuhn v Merckx, Jonas | 7-5,6-4 |
| ITF Germany F10 | 2018/07/31 14:55 | Botic Van De Zandschulp v Merckx, Jonas | 6-1,6-2 |
| ITF Belgium F5 | 2018/07/27 12:00 | Zizou Bergs v Merckx, Jonas | 6-2,6-4 |
| ITF Belgium F5 | 2018/07/26 09:00 | Merckx, Jonas v Gerritsen, Stephan | 6-2,6-0 |
| ITF Belgium F5 | 2018/07/25 12:10 | Merckx, Jonas v Fetisleam, Edris | 6-2,5-7,6-3 |
| ITF Belgium F5 | 2018/07/24 08:00 | Merckx, Jonas v Michalis Sakellaridis | 6-3,6-1 |
| ITF Belgium F4 | 2018/07/21 12:30 | Merckx, Jonas v Samuel Brosset | 4-6,5-7 |
| ITF Belgium F4 | 2018/07/20 10:00 | Merckx, Jonas v Franco Emanuel Egea | 4-6,6-4,6-0 |