The club noted that Coutinho suffered an injury to the lateral meniscus in his left knee Tuesday against Eibar. As a result, he will undergo arthroscopic surgery "in the coming days."
Coutinho, 28, is in his third season with Barca but spent last season at Bayern Munich on loan.
Coutinho has been relatively productive in his return to Barcelona this season with three goals and two assists in 14 appearances, giving him a total of 24 goals in his three seasons with the club.
The former Inter Milan and Liverpool star's absence could be significant for a Barca side that has performed well below expectations this season.
Blaugrana are just sixth in the La Liga standings with seven wins, four losses and four draws. They trail Atletico Madrid and Real Madrid by seven points.
Barcelona aren't used to being so far down the table, having won 26 La Liga titles, including 10 since 2005.
Coutinho came off the bench for Miralen Pjanic against Eibar, and there will be more pressure on the likes of Pjanic to perform while Coutinho is out.
Barcelona, who have not provided a timetable for Coutinho's return, are scheduled to face Huesca in their next match on Sunday.