Barcelona will be barred from signing any players in 2015.
FIFA has rejected the club's appeal against a one-year ban for breaching rules over the transfer of youngsters.
The Spanish giants signed 10 players under the age of 18 to the club's renowned La Masia academy.
FIFA found the signings to have violated rules designed to prevent child trafficking.
Barcelona launched an appeal against the transfer embargo in April, the ban was temporarily lifted during the current transfer window, which closes on September 1st.
That allowed Barcelona to spend around $240 million US dollars during the summer to strengthen its squad.
The ban will start during the next transfer window, early next year, which means the summer acquisitions are unaffected.
And the club can, if it wants, sign more players before the current transfer window ends.
