Stadium: Court C Round: 45
| Challenger Segovia Qual | 2018/07/29 14:30 | Karim-Mohamed Maamoun v Frederik Nielsen | 7-6,3-6,6-2 |
| Challenger Segovia Qual | 2018/07/28 12:45 | Alexander Zhurbin v Frederik Nielsen | 2-6,3-6 |
| Challenger Nottingham | 2018/06/12 15:55 | Adrian Menendez-Maceiras v Frederik Nielsen | 6-4,7-6 |
| Challenger Nottingham Qual | 2018/06/11 10:00 | Dominik Koepfer v Frederik Nielsen | 6-1,4-6,1-6 |
| Challenger Nottingham Qual | 2018/06/10 12:25 | Frederik Nielsen v Austin Krajicek | 6-3,7-6 |
| Challenger Nottingham Qual | 2018/06/09 16:45 | Frederik Nielsen v Daniil Zarichanskiy | 6-3,6-1 |
| Challenger Loughborough | 2018/05/22 12:30 | Frederik Nielsen v David Guez | 2-6,4-6 |
| Challenger Loughborough Qual | 2018/05/21 09:30 | Johannes Haerteis v Frederik Nielsen | 6-7,1-6 |