A Burnley fan was stabbed, and four others injured, outside the Georgios Karaiskakis Stadium ahead of the club's Europa League tie at Olympiakos.
The club confirmed the 22 supporters were detained in Athens following disorder were released without charge.
More than 900 Clarets fans attended the qualifying play-off first leg in Piraeus, Athens, which saw Sean Dyche's side lose 3-1.
"The vast majority were once again impeccably behaved with the coaching operation to transport supporters to the ground put in place by the club again a great success, as it was in the previous round in Istanbul," the club said in a statement.
But Burnley confirmed one supporter received a stab wound to the leg and received medical treatment at the stadium.
Burnley said they were working closely with Olympiakos and local police to investigate the incidents.
Dyche's side were unbeaten in their first European venture in 61 years prior to the game, having beat Istanbul Basaksehir and Scottish Premiership runners-up Aberdeen in extra-time in the previous qualifying rounds.