The 20-year-old moved to Camp Nou from Borussia Dortmund in the summer transfer window for a reported £97m fee.
The Frenchman's career move has not got off to the best start, though, as he was withdrawn 25 minutes into his full league debut in Saturday's 2-1 win over Getafe with a thigh problem.
It has since been confirmed by the Spanish club that the forward ruptured his tendon in the femoral bicep in his left thigh and will undergo surgery in Finland in the coming days.
A statement on Barcelona's official website revealed that Dembele is "expected to be out for between three-and-a-half months and four months", meaning that he will miss the club's remaining Champions League group-stage fixtures.
The club currently sit at the top of the La Liga standings after winning their first four top-flight fixtures.