The Scottish club has been handed the punishment as those supporting the team at the away game against Udinese exhibited an 'offensive banner' and set of fireworks in the crowd.
Celtic has been fined over $33,000 (€25,000) by UEFA after the club's fans were seen to be misbehaving during December’s 1-1 draw against Udinese in the Europa League.
The traveling fans were seen to be setting off fireworks as well as brandishing an “offensive banner” during the match. The Scottish club has not appealed the punishment.
"Celtic have been fined 25,000 euros by UEFA's control and disciplinary body for breaching Article 11 of the UEFA disciplinary regulations," a UEFA spokesman said.
"The decision was taken on Feb. 23. It is nothing out of the ordinary that it wasn't announced then. We can have 100 cases at the monthly meetings. Celtic did not appeal."
The banner was in reaction to a previous charge which saw the club fined $20,000 for illicit chanting in its game against Rennes.
Officials at Celtic stressed that the minority responsible were not a correct representative of the club’s support.
"My only surprise is that they got the spelling [on the banner] right," manager Neil Lennon said. "I am very disappointed, they have let me down, they have let the board, players and background staff down and 99.9% of the support down."
Chief executive Peter Lawwell also attempted to distance the club from such fans, saying, "It is very frustrating. Those people are not Celtic supporters.
"We will weed them out and these guys will not get back into Celtic Football Club. One or two silly little juvenile boys doing funny kids' pranks and stuff is bringing the whole of Scottish football down."