The 2018 AFC Cup knockout stage was played from 7 May to 27 October 2018.[1] A total of 11 teams competed in the knockout stage to decide the champions of the 2018 AFC Cup.[2]
The following teams advanced from the group stage:
| Key to colours | |
|---|---|
| Teams which enter the Inter-zone play-off semi-finals | |
| Teams which enter the Zonal semi-finals |
| width=120 | Zone | Group | width=200 | Winners | width=200 | Best runners-up |
|---|---|---|---|---|---|---|
| West Asia Zone | A |  Al-Jazeera | bgcolor=#BBF3FF rowspan=3 |  Al-Quwa Al-Jawiya | ||
| B | Al-Ahed | |||||
| C | Al-Faisaly | |||||
| Central Asia Zone | D |  Altyn Asyr | — | |||
| South Asia Zone | E |  Bengaluru | — | |||
| ASEAN Zone | F | Home United | bgcolor=#BBF3FF rowspan=3 | Ceres–Negros | ||
| G | Yangon United | |||||
| H |  Persija Jakarta | |||||
| East Asia Zone | I |  April 25 | — |
In the knockout stage, the 11 teams played a single-elimination tournament. Each tie was played on a home-and-away two-legged basis, except the final which was played as a single match. The away goals rule (for two-legged ties), extra time (away goals do not apply in extra time) and penalty shoot-out were used to decide the winner if necessary (Regulations Article 11.3).[2]
The schedule of each round was as follows (W: West Asia Zone; A: ASEAN Zone).[1] Matches in the West Asia Zone were played on Mondays and Tuesdays, while matches in the ASEAN Zone and the Inter-zone play-offs were played on Tuesdays and Wednesdays.
| Round | First leg | Second leg | |
|---|---|---|---|
| Zonal semi-finals | 7–9 May 2018 (W, A) | 14–16 May 2018 (W, A) | |
| Zonal finals | 1 August 2018 (A), 18 September 2018 (W) | 8 August 2018 (A), 2 October 2018 (W) | |
| Inter-zone play-off semi-finals | 21–22 August 2018 | 28–29 August 2018 | |
| Inter-zone play-off final | 19 September 2018 | 3 October 2018 | |
| Final | 27 October 2018 | ||
The bracket of the knockout stage was determined as follows:
| Round | Matchups | |
|---|---|---|
| Zonal semi-finals | (Matchups and order of legs determined by identity of best runners-up: first team listed host first leg, second team listed host second leg)
| |
| Zonal finals | (Order of legs decided by draw)
| |
| Inter-zone play-off semi-finals | (Matchups and order of legs decided by draw, involving Winner Group D, Winner Group E, Winner Group I, and Winner AF)
| |
| Inter-zone play-off final | (Winner IZSF1 host first leg, Winner IZSF2 host second leg)
| |
| Final | (Winner WF host match, as alternated from previous season's final)
|
In the Zonal semi-finals, the four qualified teams from the West Asia Zone (Groups A–C) played in two ties, and the four qualified teams from the ASEAN Zone (Groups F–H) played in two ties, with the matchups and order of legs determined by the group stage draw and the identity of the best runners-up.
|+West Asia Zone|+ASEAN Zone
Al-Jazeera won 2–1 on aggregate.----Al-Quwa Al-Jawiya won 5–3 on aggregate.
Home United won 6–3 on aggregate.----Ceres–Negros won 6–5 on aggregate.
The draw for the Zonal finals was held on 23 May 2018.[5] In the Zonal finals, the two winners of West Asia Zonal semi-finals played each other, and the two winners of ASEAN Zonal semi-finals played each other, with the order of legs decided by draw. The winners of the West Asia Zonal final advanced to the final, while the winners of the ASEAN Zonal final advanced to the Inter-zone play-off semi-finals.
|+West Asia Zone|+ASEAN Zone
Al-Quwa Al-Jawiya won 4–1 on aggregate.
Home United won 3–1 on aggregate.
The draw for the Inter-zone play-off semi-finals was held on 23 May 2018.[5] In the Inter-zone play-off semi-finals, the four zonal winners other than the West Asia Zone played in two ties, i.e., the winners of the Central Asia Zone (Group D), the winners of the South Asia Zone (Group E), the winners of the East Asia Zone (Group I), and the winners of the ASEAN Zonal final (whose identity was not known at the time of the draw), with the matchups and order of legs decided by draw, without any seeding.
April 25 won 11–1 on aggregate.----Altyn Asyr won 5–2 on aggregate.
In the Inter-zone play-off final, the two winners of the Inter-zone play-off semi-finals played each other, with the order of legs determined by the Inter-zone play-off semi-final draw. The winners of the Inter-zone play-off final advanced to the final.
3–3 on aggregate. Altyn Asyr won on away goals.
See main article: article and 2018 AFC Cup Final. In the final, the winners of the West Asia Zonal final and the winners of the Inter-zone play-off final played each other, with the host team (winners of the West Asia Zonal final) alternated from the previous season's final.[6]