Todibo spent the second half of the 2020/2021 season at the Allianz Riviera stadium and made 15 appearances in the French top flight as Nice finished ninth on the table.
The 21-year-old Frenchman will remain with Nice after the club agreed an initial £7m fee with Barcelona.
Todibo joined Barcelona on a free transfer from Toulouse in the January 2019 but he made just five appearances in his time at the Camp Nou and was loaned out to the likes of Schalke 04 and Benfica before returning to France.
Barcelona have confirmed Todibo's departure in an official statement on their website, which reads: "OGC Nice has reported to FC Barcelona that it shall exercise its right to purchase Jean-Clair Todibo, who has been playing on loan to the French club since the end of the 20/21 season.
"The operation is valued at 8.5 million euros, plus a further 7 million euros in variables. The Catalan club withholds a percentage on any future sale of the player.
"FC Barcelona wishes to publicly state its gratitude to Jean-Clair Todibo for his commitment and dedication and wishes him all the very best of success in the future."
Nice welcomed Todibo with a statement of their own which read: "OGC Nice and FC Barcelona have agreed terms for the permanent transfer of Jean-Clair Todibo! He said it right from the start: 'In my mind, I will be at OGC Nice next season. And the one after that as well!'
"Following a six-month loan, where his performances impressed everyone, Jean-Clair Todibo (21-years-old) has officially signed for Les Aiglons, confirming his first words on the Cote d’Azur.
"Now he is officially back home, to continue his progression, both individually and with the team."
