Barcelona have been given a fine of €110,000 (£87,125) by UEFA after fans used flares to celebrate their Super Cup victory over Porto in Monaco at the end of August.
Goals from Lionel Messi and Cesc Fabregas secured the win in the annual match which pits the Champions League winners and Europa League winners against each other.
The trophy was Barca's second of this campaign after their Spanish Super Cup win against rivals Real Madrid.
The Catalan club have ten days to appeal the decision.