Barcelona have been given a 14-month transfer ban for breaking rules on signing international players under 18.
The Catalan club cannot buy players until the summer of 2015 after the world governing body, Fifa, imposed a transfer ban for the next two windows.
The Spanish champions have also been fined 450,000 Swiss Francs (£305,000) and have confirmed they will appeal.
The Spanish Football Federation (RFEF) has been sanctioned by Fifa for the same breaches.
Barcelona, who will still be allowed to sell players, are hoping to sign a new goalkeeper at the end of the season, with the long-serving Victor Valdes leaving the Nou Camp at the end of his contract.
Any appeal against the ban must be lodged within three days and is not likely to be heard until April.
"FCB will present the corresponding appeal to Fifa and if necessary will submit the resulting resolution to the Court of Arbitration for Sport (CAS)," said a statement on the club's official website.
Should the case reach CAS it would raise the possibility that the club could still sign players this summer if the ban is not imposed until a final decision is made.
The RFEF has been given a fine of 500,000 Swiss Francs (£340,000) and told to "regularise its regulatory framework and existing system concerning the international transfer of minors in football" within a year.
Fifa rules state that international transfers are only permitted for players over the age of 18 - unless the player in question meets one of three qualifying criteria.
Under-18s can move to a club in a different country if their parents move there for non-footballing reasons, if they are from another nation within the European Union or European Economic Area and aged between 16 and 18, or if they live within 100km of the club.
A Fifa investigation - centred on several players aged under 18 who were registered and played for the club between 2009 and 2013 - found that Barcelona and the RFEF were guilty of a "serious" infringement of the rules in relation to 10 players.
Fifa told BBC Sport the identity of these players was confidential.
Its disciplinary committee said it sought to protect the best interests of young players, even if an international transfer might be beneficial to their football careers.
"On the basis of this analysis, the committee concluded that 'the interest in protecting the appropriate and healthy development of a minor as a whole must prevail over purely sporting interests'," said a Fifa statement.
It is the latest off-the-field issue to trouble Barcelona this season.
Earlier this year, the Catalan club were accused by the Spanish authorities of tax evasion relating to the £50m purchase of Brazil forward Neymar. A criminal investigation is under way, despite Barca making a "voluntary contribution" of more than £11m in taxes.
The club's president Sandro Rosell resigned after he was accused of misappropriating funds in the deal.
Rosell and his successor Josep Maria Bartomeu insist the 22-time Spanish champions have not acted illegally.