| Challenger Columbus | 01/07 15:00 | 166 | [449] Gijs Brouwer v Mertens, Yannick [410] | 6-3,6-3 | |
| Challenger Canberra 2 | 10/30 04:05 | 25 | [325] Mertens, Yannick v Rubin Statham [271] | 3-6,7-6,5-7 | |
| Challenger Traralgon | 10/24 00:25 | 26 | [336] Mertens, Yannick v Alex Bolt [140] | 5-7,1-6 | |
| Challenger Traralgon | 10/23 00:30 | 25 | Mertens, Yannick v Bourchier, Harry | 6-3,6-7,7-6 | |
| Antwerp, Belgium | 10/14 12:50 | 64 | [94] Granollers, Marcel v Mertens, Yannick [335] | 6-4,6-4 | |
| ITF Portugal F18 | 09/30 10:00 | 29 | [275] Gleb Sakharov v Mertens, Yannick [357] | 7-6,6-4 | |
| ITF Portugal F18 | 09/29 12:25 | 28 | [479] Cacao, Tiago v Mertens, Yannick [357] | 4-6,1-6 | |
| ITF Portugal F18 | 09/28 14:00 | 27 | [284] Marek Gengel v Mertens, Yannick [357] | 6-2,6-7,1-6 | |
| ITF Portugal F18 | 09/27 09:00 | 26 | Pedro Araujo v Mertens, Yannick | 2-6,3-6 | |
| ITF Portugal F18 | 09/26 10:20 | 25 | [446] Dischinger, Eduardo v Mertens, Yannick [357] | 0-6,6-7 | |
| ITF France F18 | 09/23 13:00 | 29 | Cornut-Chauvinc, Antoine v Mertens, Yannick | 6-7,2-6 | |
| ITF France F18 | 09/22 13:50 | 28 | [395] Antoine Escoffier v Mertens, Yannick [352] | 6-7,6-3,6-7 | |
| ITF France F18 | 09/21 10:30 | 27 | [449] Avidzba, Alen v Mertens, Yannick [352] | 1-6,0-6 | |
| ITF France F18 | 09/19 11:35 | 26 | Sora Fukuda v Mertens, Yannick | 3-6,4-6 | |
| ITF France F18 | 09/18 09:35 | 25 | Bourcet, Tony v Mertens, Yannick | 4-6,2-6 | |
| ITF France F16 | 09/07 09:20 | 27 | Mertens, Yannick v Albano Olivetti | 1-6,5-7 | |
| ITF France F16 | 09/05 09:00 | 26 | Mertens, Yannick v Petit, Gabriel | 6-4,6-4 | |
| ITF France F16 | 09/04 10:15 | 25 | Mertens, Yannick v Constantin B Kouzmine | 4-6,6-4,6-4 | |
| Challenger Mallorca | 08/26 10:45 | 45 | [349] Mertens, Yannick v Simon, Tobias [444] | 7-6,4-6,4-6 | |
| ITF Netherlands F4 | 08/16 10:30 | 26 | Mertens, Yannick v Kazuki Nishiwaki | 3-6,6-7 | |
| ITF Netherlands F4 | 08/14 14:15 | 25 | Mertens, Yannick v Sidane Pontjodikromo | 6-1,4-6,6-4 | |
| Challenger Pullach Qual | 08/04 15:25 | 45 | [349] Mertens, Yannick v Steven Diez [316] | 2-6,2-6 | |
| Challenger Astana | 07/17 07:45 | 25 | [362] Mertens, Yannick v Jurij Rodionov [284] | 5-7,0-6 | |
| ITF France F13 | 07/13 17:20 | 27 | [348] Mertens, Yannick v Sora Fukuda [493] | 6-2,3-6,4-6 | |
| ITF France F13 | 07/12 18:30 | 26 | [348] Mertens, Yannick v Lakat, Florian [280] | 6-3,6-4 | |
| ITF France F13 | 07/10 13:40 | 25 | [348] Mertens, Yannick v Voljacques, Hugo [306] | 6-2,6-2 | |
| Challenger Recanati Qual | 07/02 10:00 | 54 | [351] Barrios Vera, Marcelo Tomas v Mertens, Yannick [348] | 7-6,6-3 | |
| Challenger Recanati Qual | 07/01 08:00 | 46 | Frigerio, Lorenzo v Mertens, Yannick | 4-6,4-6 | |
| Challenger Recanati Qual | 06/30 11:15 | 45 | Vernier, Michel v Mertens, Yannick | 2-6,4-6 | |
| ATP Eastbourne Qual | 06/23 14:35 | 64 | [344] Mertens, Yannick v Quiroz, Roberto [244] | 6-3,4-6,3-6 |