Barcelona have a deal to sign Miralem Pjanic from Juventus for an initial €60million, with Arthur having agreed to move in the opposite direction in a separate arrangement.
Pjanic will put pen to paper on a four-year contract with Barca and join them at the conclusion of the 2019-20 campaign. The transfer includes an additional €5m in variables.
Earlier on Monday, LaLiga's champions confirmed Arthur will join Juve from next season for an initial €72m. The Bianconeri are yet to reveal the details of the Brazil international's contract.
Bosnia-Herzegovina international Pjanic is seven years Arthur's senior and has been at Juve since a switch from Roma in 2016.
The set-piece specialist has remained an integral part of the team since Maurizio Sarri replaced Massimiliano Allegri as head coach for this season, although he arguably does not entirely meet the ex-Napoli and Chelsea boss' very specific demands for his holding midfielder.
Pjanic has won Serie A in each of his three completed seasons in Turin, scoring 22 times in 171 appearances across all competitions.
He is well-placed to make it four in a row, with Juve four points clear of Lazio in this season's Scudetto race, although Barcelona's plans to freshen up their midfield are perhaps partially explained by them falling two points shy of Real Madrid at the top of LaLiga – meaning Arthur might struggle to leave as a back-to-back champion.