| 1. Round | 14/08/2020 | NK Opatija | - | Hajduk Split II | 2:1 | ||||
| 2. Round | 22/08/2020 | NK Sesvete | - | NK Opatija | 0:1 | ||||
| 4. Round | 12/09/2020 | NK Rudeš | - | NK Opatija | 1:2 |  |
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| 5. Round | 15/09/2020 | NK Opatija | - | HNK Cibalia | 0:1 | ||||
| 6. Round | 19/09/2020 | NK Dubrava | - | NK Opatija | 1:4 |  |
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| 12. Round | 30/10/2020 | NK Međimurje | - | NK Opatija | 3:0 | ||||
| 13. Round | 25/11/2020 | NK Opatija | - | NK Inter Zaprešić | 3:2 | ||||
| 19. Round | 20/02/2021 | NK Opatija | - | NK Sesvete | 1:0 | ||||
| 22. Round | 14/03/2021 | HNK Cibalia | - | NK Opatija | 2:0 | ||||
| 26. Round | 17/04/2021 | NK Osijek II | - | NK Opatija | 1:0 | ||||
| 27. Round | 21/04/2021 | NK Opatija | - | NK Junak Sinj | 1:0 | ||||
| 28. Round | 24/04/2021 | NK Dugopolje | - | NK Opatija | 0:0 | ||||
| 25. Round | 28/04/2021 | NK Opatija | - | Hrvatski Dragovoljac | 0:0 | ||||
| 29. Round | 01/05/2021 | NK Opatija | - | NK Međimurje | 1:1 | |
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| 30. Round | 07/05/2021 | NK Inter Zaprešić | - | NK Opatija | 3:0 | ||||
| 34. Round | 29/05/2021 | NK Opatija | - | NK BSK Bijelo Brdo | 2:2 |
Croatia