FIFA published news of its decision on its official website, saying the ban was the result of Barcelona carrying out "breaches relating to the international transfer and registration of players under the age of 18", reports Xinhua.
FIFA explained that both Barcelona and the Spanish Football Federation (RFEF) had "violated several provisions concerning the international transfer and first registration of non-Spanish minors with the club," over the period 2009 to 2013.
The organisation highlighted that its Disciplinary Committee believes that while in some cases international transfers may be positive for players aged under 18, it is generally "contrary to the best interests of the player as a minor."
FIFA has found Barca to have broken their rules with 10 young players and to have committed "other concurrent infringements in the context of other players."
As a result FC Barcelona have been prohibited from signing any new players over the "next two transfer windows," effectively stopping them buying anyone either this summer or in January 2015.
The club has also been fined 450,000 Swiss Francs ($508,000) and given 90 days to bring the situation of the 10 players in order.
The RFEF meanwhile was fined 500,000 Swiss Francs and given a year in which to improve their framework for controlling the international transfers of minors.
Although Barca are certain to appeal against the decision, it is a huge blow for the club which had looked certain to be one of the big movers in the summer transfer window after goalkeeper Victor Valdes and veteran defender Carles Puyol both announced they would leave at the end of the season.
Barcelona are thought to have agreed to a deal to bring in Borussia Monchengladbach goalkeeper Ter Stegen to replace Valdes, while they need to sign at least one central defender and possibly a new right back and central midfielder.
If they are unable to have the ban overturned in order to make these signings the club will now have to fill the gaps with young players from its B-team, which would obviously weaken the first team squad for the 2014-15 campaign.