The Spanish club were bidding to overturn a two-window suspension handed out by FIFA in April after they were found to have breached rules on signing international players under the age of 18.
After losing a FIFA appeal in August, they took the case to CAS, the highest sporting authority, but their appeals panel found no grounds to overturn the original ruling.
It means Barcelona boss Luis Enrique will be unable to bring in any new blood until January 2016.
“The Court of Arbitration for Sport (CAS) has dismissed the appeal filed by FC Barcelona against the Federation Internationale de Football Association (FIFA) regarding the decision issued by the FIFA appeals committee on 19 August 2014,” a statement from CAS read.
“In such decision, the Spanish football club was sanctioned with a transfer ban for two periods, a fine of CHF 450,000 and a reprimand after it was found to have infringed the FIFA regulations with respect to the registration of a number of minor players.”
Barcelona were found guilty of breaching FIFA’s rules on the transfer of players aged under 18.
The players in question were registered and participated in competitions with the Catalan club between 2009 and 2013.
The CAS statement continued: “The panel found in particular that FC Barcelona had breached the rules regarding the protection of minors and the registration of minors attending football academies (articles 19 and 19bis of the FIFA regulations on the status and transfer of players).
“Accordingly, the FIFA decision is confirmed in full and the sanction remains in force. In view of the need to issue a decision before the opening of the next transfer window, the panel has issued its decision without the grounds. The full arbitral award, with the reasons for the panel’s decision, will be issued as soon as possible.”
Barca went on a summer spending spree this year while the suspension went on hold during the appeals process, splashing out more than 150million euros on Luis Suarez, Ivan Rakitic, Marc-Andre ter Stegen, Thomas Vermaelen, Claudio Bravo, Jeremy Mathieu and Alen Halilovic.
But there will be no further new recruits heading to the Nou Camp for at least 12 months, with the CAS ruling the final word on the matter.