| 9. Round | 23/10/1998 | Antalyaspor | - | İstanbulspor AŞ | 2:3 |  |
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| 10. Round | 30/10/1998 | İstanbulspor AŞ | - | Gaziantepspor | 0:0 | ||||
| 11. Round | 07/11/1998 | Altay Izmir | - | İstanbulspor AŞ | 2:1 | ||||
| 12. Round | 14/11/1998 | İstanbulspor AŞ | - | Bursaspor | 2:3 | |
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| 13. Round | 20/11/1998 | Kocaelispor | - | İstanbulspor AŞ | 0:1 | ||||
| 14. Round | 27/11/1998 | İstanbulspor AŞ | - | Dardanelspor | 1:1 | ||||
| 15. Round | 04/12/1998 | Erzurumspor (1968-2015) | - | İstanbulspor AŞ | 2:4 | ||||
| 27. Round | 10/04/1999 | Gaziantepspor | - | İstanbulspor AŞ | 2:1 | ||||
| 28. Round | 16/04/1999 | İstanbulspor AŞ | - | Altay Izmir | 3:0 | ||||
| 29. Round | 24/04/1999 | Bursaspor | - | İstanbulspor AŞ | 2:0 | ||||
| 30. Round | 01/05/1999 | İstanbulspor AŞ | - | Kocaelispor | 2:1 | ||||
| 31. Round | 09/05/1999 | Dardanelspor | - | İstanbulspor AŞ | 5:1 | ||||
| 32. Round | 15/05/1999 | İstanbulspor AŞ | - | Erzurumspor (1968-2015) | 0:2 | ||||
| 33. Round | 22/05/1999 | İstanbulspor AŞ | - | Fenerbahçe | 1:2 | ||||
| 34. Round | 29/05/1999 | Gençlerbirliği | - | İstanbulspor AŞ | 2:3 |
Turkey