The Court of Arbitration for Sport has dismissed Barcelona's appeal and upheld the transfer ban FIFA imposed on the club for infringing regulations on registering minors as youth players.
CAS says Tuesday that Barcelona "breached the rules" governing the protection of minors and the registration of those attending football academies.
The ruling means Barcelona won't be allowed to sign players during the next two transfer windows, although it can renew contracts and recall players ceded to other clubs, such as Denis Suarez and Gerard Deulofeu, both at Sevilla.
Barcelona said in a statement it totally disagreed with the ruling and considered the sanction "completely disproportionate."
The club said it was evaluating legal options, including appealing the decision to the Swiss Federal Court.