Stadium: Court 6 Round: 62 Ground: Clay
| ITF M25 Kottingbrunn | 2021/07/19 12:25 | Peter Goldsteiner v Martin Zeljenka | 6-4,7-6 |
| ITF M25 Kottingbrunn | 2021/07/18 07:30 | Martin Zeljenka v Rafael Kis Balazs | 2-6,6-4,10-2 |
| ITF M25 Belgrade | 2021/06/29 07:00 | Bogdan Pavel v Martin Zeljenka | 6-1,6-3 |
| ITF M25 Belgrade | 2021/06/28 10:00 | Martin Zeljenka v Matvey Minin | 7-5,6-3 |
| ITF M25 Belgrade | 2021/06/27 12:00 | Martin Zeljenka v George Gregoriou | 6-1,6-1 |
| ITF M15 Sibenik | 2021/05/17 11:00 | Martin Zeljenka v Martin Breysach | 6-7,3-6 |
| ITF M15 Sibenik | 2021/05/16 07:30 | Joris Hoogland v Martin Zeljenka | 6-7,3-6 |
| ITF M15 Prijedor | 2021/05/09 09:30 | Kristijan Juhas v Martin Zeljenka | 6-1,6-1 |
| ITF M15 Doboj | 2021/07/13 08:00 | Kristof Minarik v Danilo Raicevic | 6-1,6-3 |
| ITF M15 Doboj | 2021/07/12 11:00 | Danilo Raicevic v Nicolas Bruna | 6-3,7-6 |