Arthur will go to Juve at the end of this season, with Pjanic arriving in the opposite direction.
The Blaugrana are set to receive a 12 million euro windfall as a result, reports Marca.
June 30 was the deadline for these two deals to appear on the balance sheets for the current fiscal year, and Barcelona were more than happy for that to be the case.
Not only do they sign a player they wanted for 2020/21 anyway, but they get to boost their fiscal records for the current year by around 12 million euros.
They also don't have to factor in the purchase of Pjanic into the accounts for the next fiscal year, which in essence allows them to, for example, pursue Lautaro Martinez once the summer transfer window begins.
Barcelona needed to make a sale before June 30 in order to balance the books, and they have now done just that.
On Monday, Pjanic had a message for the Barcelona fans on social media.
"I'm so happy," Pjanic said. "I'll give everything for this club. See you soon. Forca Barca!"