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.
The Bosnian has signed a deal with Barcelona for the next four seasons, with that deal including a release clause of €400 million (£366 million/$449 million).
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.