| Prevseason: | 2019 |
| Nextseason: | 2022 |
The 2021 Durand Cup knockout stage began on 23 September with the quarter-finals and ended on 3 October 2021 with the final at the Vivekananda Yuba Bharati Krirangan in Kolkata, West Bengal, to decide the champions of the 2021 Durand Cup.[1] A total of 8 teams competed in the knockout phase.
The knockout stage involves the eight teams which qualified as winners and runners-up of each of the four groups in the group stage.
Indian Super League club
I League club
2nd Division League club
Indian Armed Forces team
The schedule was as follows.
| Round | Dates | |
|---|---|---|
| Quarter-finals | 23–25 September 2021 | |
| Semi-finals | 27–29 September 2021 | |
| Final | 3 October 2021 |
| Mohammedan | 1–0 | Gokulam Kerala | |
| Army Red | w/o | Bengaluru United | |
| Goa | 5–1 | Delhi | |
| Bengaluru | 3–2 | Army Green |
| Mohammedan | 4–2 (a.e.t) | Bengaluru United | |
| Goa | 2–2 (7-6 pen.) | Bengaluru |
See main article: 2021 Durand Cup Final. The final was played on 3 October 2021 at the Vivekananda Yuba Bharati Krirangan in Kolkata.