Stadium: Court 13 Round: 54 Ground: Carpet indoor
| ITF Germany F1 | 2018/01/08 12:30 | Karlo Cubelic v Kai Lemstra | 6-4,2-6,4-6 |
| ITF M15 Forbach | 2020/09/30 08:30 | Kai Lemstra v Alexander Erler | 3-6,2-6 |
| ITF M15 Forbach | 2020/09/28 15:45 | Kai Lemstra v Niklas Schell | 6-4,7-6 |
| ITF M15 Anif | 2020/08/26 14:40 | Karlis Ozolins v Kai Lemstra | 7-5,6-3 |
| ITF M15 Anif | 2020/08/24 12:50 | Kai Lemstra v Benedikt Emesz | 6-1,6-2 |
| ITF M15 Anif | 2020/08/23 12:00 | Kirill Kivattsev v Kai Lemstra | 6-7,3-6 |
| ITF M15 Sharm El Sheikh | 2020/03/11 11:40 | Francesco Vilardo v Kai Lemstra | 6-4,6-7,7-5 |
| ITF M15 Trnava | 2020/02/27 12:10 | Kai Lemstra v Aldin Setkic | 3-6,3-6 |
| ITF M15 Trnava | 2020/02/26 12:10 | Kai Lemstra v Andrej Glvac | 6-4,6-4 |
| ITF M15 Sarreguemines | 2020/10/25 16:20 | Karlo Cubelic v Adil Kalyanpur | 6-2,6-3 |
| ITF M15 Forbach | 2020/09/30 08:30 | Karlo Cubelic v Daniele Capecchi | 1-6,6-1,5-7 |
| ITF M15 Forbach | 2020/09/28 14:00 | Alafia Ayeni v Karlo Cubelic | 7-5,4-6,8-10 |
| ITF M15 Forbach | 2020/09/28 07:00 | Pol Amoros Ramos v Karlo Cubelic | 1-6,5-7 |
| German Masters | 2020/08/28 13:15 | Daniil Glinka v Karlo Cubelic | 6-4,3-6,4-6 |
| German Premier League | 2020/08/27 06:30 | Karlo Cubelic v Alexander Mannapov | 6-1,6-2 |
| German Premier League | 2020/08/26 10:50 | Inigo C Huegun v Karlo Cubelic | 3-6,1-6 |
| German Premier League | 2020/08/25 15:50 | Altug Celikbilek v Karlo Cubelic | 6-3,7-6 |