^Laos (LAO): Laos originally had one entry: Lao Toyota, the 2017 Lao Premier League champions. However, on 14 December 2017, the AFC announced that they were ruled ineligible to play in the 2018 AFC Cup due to match manipulation during the 2015 and 2016 AFC Cup.[6] As they were the only team from Laos which obtained an AFC licence, no other teams were eligible to replace them.[3] Lao Toyota appealed the decision to the Court of Arbitration for Sport (CAS), and on 17 January 2018, CAS ruled Lao Toyota would be eligible to participate.[7]
^Macau (MAC): Macau had only one entry, as only one team obtained an AFC licence.[3]
^Malaysia (MAS): Malaysia had only one entry as Pahang, the 2017 Malaysia Super League runners-up, which would have entered the group stage, decided not to participate in the AFC Cup after obtaining an AFC licence, and as a result, the second group stage slot for Malaysia was annulled and could not be filled by any other team from Malaysia (Entry Manual 12.12).[8][4][9][10][11]
^Nepal (NEP): Nepal did not comply with the AFC Cup club licensing system.[3]
^AFC Champions League (ACL): Teams played in the AFC Champions League qualifying play-offs, but failed to advance to the AFC Champions League group stage. Had they advanced to the AFC Champions League group stage, they would not have played in the AFC Cup and would have been replaced in the AFC Cup group stage by the standby team from the same association if such team was available.
^Bangladesh (BAN):Sheikh Jamal, the 2017–18 Bangladesh Premier League runners-up, failed to obtain an AFC license. As a result, Saif, the league 4th place and the highest-placed team with an AFC license not yet qualified, entered the qualifying play-offs.[13]
^Chinese Taipei (TPE):Tatung and Taipower, the 2017 Taiwan Premier League champions and runners-up, failed to obtain an AFC license. As a result, Hang Yuen, the league 3rd place and the only team with an AFC license, entered the group stage.[14][3]
^Indonesia (IDN):Bhayangkara, the 2017 Indonesia League 1 champions, failed to obtain an AFC license. As a result, Persija Jakarta, the league 4th place and the highest-placed team with an AFC license not yet qualified, entered the group stage.[15]
^Vietnam (VIE):Quảng Nam, the 2017 V.League 1 champions, failed to obtain an AFC licence. As a result, FLC Thanh Hóa, the league runners-up, entered the group stage.[16]