Stadium: Court 5 Round: 26 Ground: Clay
| Challenger Alicante MD | 2018/04/06 14:45 | Koolhof/Sitak v Andreozzi/Behar | 6-3,6-2 |
| Challenger Alicante MD | 2018/04/05 09:30 | Koolhof/Sitak v Martinez Portero/Vega Hernandez | 5-7,6-4,10-5 |
| Challenger Alicante MD | 2018/04/02 12:35 | Koolhof/Sitak v Cervantes/Marrero | 6-4,6-1 |
| Challenger Irving MD | 2018/03/16 23:10 | Petzschner/Peya v Koolhof/Sitak | 6-4,7-5 |
| Challenger Irving MD | 2018/03/15 22:25 | Koolhof/Sitak v Krajicek/Lacko | 6-1,6-4 |
| Challenger Irving MD | 2018/03/14 19:00 | Inglot/Skupski v Koolhof/Sitak | 6-3,1-6,6-10 |
| ATP Sao Paulo MD | 2018/03/04 17:20 | Koolhof/Sitak v Delbonis/Gonzalez | 4-6,2-6 |
| ATP Sao Paulo MD | 2018/03/03 20:00 | Berlocq/Kicker v Koolhof/Sitak | 3-6,3-6 |