Sporting Lisbon say they want 57 million euros (£50m) in compensation for Portugal goalkeeper Rui Patricio following his transfer to Wolves.
The Portuguese club, who say the 30-year-old “broke his contract” when he joined the newly promoted side in June, have officially complained to Fifa.
Patricio is one of nine Sporting players to terminate their contracts with the Primeira Liga club.
“Patricio left the club without previous agreement,” said Sporting.
Fifa told BBC Sport it had received a complaint from Sporting against Wolves and Patricio.
Wolves have declined to comment.
A group of 50 fans reportedly attacked Sporting players and staff in May after the club missed out on a Champions League place on the final day of the season.
In April, former Sporting president Bruno de Carvalho claimed to have suspended 19 first-team players after a Europa League defeat by Atletico Madrid, although he deleted the post on social media and most of the players featured in their next game.
De Carvalho has since quit the club after fans voted for him to resign, with Sousa Cintra put in temporary charge until elections are held in September.
Sinisa Mihajlovic, De Carvalho’s managerial appointment, was sacked after nine days and replaced by Jose Peseiro, who has returned for his second spell at the club.