Brazilian winger Malcom has passed a medical at Barcelona before his £36.5m move from Bordeaux.
The deal was announced on Tuesday after the Spanish champions beat Roma to the signature of the 21-year-old.
“This is a boyhood dream come true,” said Malcom, who is yet to be capped by Brazil. “I can’t wait to get started.”
Roma are considering whether they have “a legal case” after reaching a deal with Bordeaux on Monday, subject to a medical and personal terms.
Barcelona will pay an initial 41m euros, with another 1m euros (£900,000) in variables.
Malcom, who scored 20 goals and set up 13 in 84 Ligue 1 games for Bordeaux, will join Barcelona on their USA tour.
He is the club’s second Brazilian summer signing, after midfielder Arthur joined from Gremio for £35.5m.
They have also signed Sevilla centre-back Clement Lenglet for 35.9 million euros (£32m).