The Catalan club cannot buy or sell players until the summer of 2015 after the world governing body
imposed a transfer ban for the next two windows.
They have also been fined 450,000 Swiss Francs (£305,000).
The Spanish Football Federation (RFEF) has been sanctioned by Fifa for the same breaches.
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.
A Fifa investigation found that Barcelona and the RFEF were guilty of a "serious" infringement of the rules in relation to 10 players.
The investigation centred on several players aged under 18 who were registered and played for the club between 2009 and 2013.
Fifa's 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
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