Luis Enrique’s side completed one of the most remarkable comebacks in Champions League history earlier this month, bouncing back from a 4-0 first leg defeat to the Ligue 1 champions.
Sergi Roberto’s decisive stoppage-time goal sparked wild celebrations in the Nou Camp, with some supporters entering the field of play after the final whistle.
Uefa, European football’s governing body, have now fined the Catalan club €19,000 for a “field invasion by supporters” contravening Art. 16 (2) of the organisation’s disciplinary regulations.
The fine also takes into account the “improper conduct of the team” after five Barcelona players were shown yellow cards during the victory.
St-Etienne, Manchester United’s Europa League round of 32 opponents, have also been fined €50,000 (£43,083) after supporters set off fireworks at the Stade Geoffroy-Guichard.
The Ligue 1 side were defeated 1-0 in the second leg, with Jose Mourinho’s United progressing to the last-16 with a 4-0 aggregate win.