| UTR Pro Tennis Series Zadar | 2021/06/29 12:30 | Kajin, Karlo v Khomich, Aleksei | 6-4,3-6,2-6 |
| UTR ProTennis Series Zadar | 2021/06/28 08:00 | Kajin, Karlo v Goetz, Ryan | 1-6,1-5 |
| ITF Croatia F3 | 2018/03/19 12:30 | Gabrieli, Tommaso v Kajin, Karlo | 7-6,6-4 |
| ITF Croatia F3 | 2018/03/18 10:30 | de Rosa, Marco v Kajin, Karlo | 6-7,6-2,2-6 |
| ITF Croatia F2 | 2018/03/12 08:00 | Andres Gabriel Ciurletti v Kajin, Karlo | 6-3,6-3 |
| ITF Croatia F2 | 2018/03/10 09:00 | Kajin, Karlo v Schlageter, Justin | 3-6,6-2,6-4 |
| ITF Croatia F1 | 2018/03/08 09:00 | Meis, Pascal v Kajin, Karlo | 6-3,6-1 |
| ITF Austria F5 | 2017/07/29 07:00 | Charles Broom v Kajin, Karlo | 6-0,6-4 |
| UTR Pro Tennis Series Zadar | 2021/06/29 14:00 | Goetz, Ryan v Kiefer, Alexander | 6-0,6-2 |