FIFA has banned Barcelona from transferring players for the next two transfer windows due to breaches relating to the international transfer and registration of players under the age of 18.
Wednesday's shock ruling means Barcelona are prevented from either buying or selling players until the summer of 2015.
Barcelona have been fined CHF 450,000 (£306,000). The Spanish FA (RFEF) was fined CHF 500,000 and given a year to regulate their systems.
FIFA said in a statement: "FC Barcelona has been found to be in breach of article 19 of the regulations in the case of 10 minor players and to have committed several other concurrent infringements in the context of other players.
"The disciplinary committee regarded the infringements as serious and decided to sanction the club with a transfer ban at both national and international level for two complete and consecutive transfer periods, together with a fine of 450,000 Swiss francs.
"Additionally, the club was granted a period of 90 days in which to regularise the situation of all minor players concerned."
The sanctions follow investigations initially conducted by the FIFA Transfer Matching System over the course of last year and subsequently by the FIFA Disciplinary Committee as part of disciplinary proceedings.
The RFEF and Barcelona were found to have violated several provisions concerning the international transfer and first registration of non-Spanish minors with the club.
The investigations concerned several minor players who were registered and participated in competitions with the club over various periods between 2009 and 2013.
Neither FIFA nor Barcelona have confirmed the identities of the players in question but in March, FIFA president Sepp Blatter spoke about potential punishments for Barcelona regarding six young players who were banned from playing for the club.
The players were: Koreans Lee Seung Woo, Paik Seung-Ho and Jang Gyeolhee, French youngster Theo Chendri, Nigerian-Dutchman Bobby Adekanye and Cameroonian Patrice Sousia.
Chelsea were given a two-window transfer ban in 2010 for irregularities over their signing of Gael Kakuta from Lens but the punishment was later removed in court.