Coutinho, 28, damaged the meniscus in his left knee after coming on as a substitute in Tuesday's draw at Camp Nou against Eibar.
Barca said Saturday's operation went well but that the Brazil international will now be sidelined for around three months.
With a condensed schedule in place this season due to the COVID-19 pandemic, Coutinho could miss up to 20 games as he recovers.
He will sit out this month's Spanish Super Cup and will be unavailable for the Champions League tie against Paris Saint-Germain.
Coutinho returned to Barcelona this season following a loan spell with Bayern Munich, where he won the treble, after coach Ronald Koeman promised him an important role in his team.
However, injuries have affected his performances and limited him to just 14 appearances in all competitions, in which time he has scored three goals.