Barcelona have agreed to sell Arthur to Juventus for €72 million (£66m/$81m), the Catalan club have confirmed on their official website.
Juve's Miralem Pjanic is set to move in the other direction, although both players will conclude the 2019-20 campaign at their current clubs.
Arthur joined the club from Gremio in 2018 and has turned out 72 times in total for the Camp Nou side, including 28 appearances in all competitions this season, during which he has scored all four of his goals for the club.
He was seen giving a speech to his team-mates at Barcelona's training session on Monday – an act that has been widely interpreted as the 23-year-old saying his goodbyes to a dressing room he joined in July 2018 from Gremio.
And head coach Quique Setien has included the player in the squad to face Atletico Madrid on Tuesday, despite the deal being close to completion.
"I have no doubt about his greatest commitment until the last day he is here," the head coach told the media.
"He is a player until the last game of the season. He has committed himself to being one more [member of the squad].
"He will dedicate himself fully to achieving the objectives. I have no doubts about him.
"He has said that he will be in the best conditions. I'll decide if he plays more or less."
Sergi Roberto is back in the Barca squad to face Atletico having sat out three matches with a fractured rib.
Two draws in their past three games have left the reigning champions two points behind Real Madrid at the top of La Liga with six matches remaining, heightening speculation that Setien will be dismissed at the end of the season despite only being in post since January.
The coach, however, has played down any concerns he has ahead of the clash with Diego Simeone's side, who lie third in the standings, though a distant 11 points short of the Catalan outfit with only six matches of the campaign remaining.
More to follow...