The France international picked up a knock during a crushing 5-1 victory over Lyon on Wednesday, having entered that contest already nursing a slight complaint.
He stepped off the bench in a Champions League clash to find the target and book a place in the quarter-finals.
A 20-minute cameo came at a cost, though, with the World Cup winner now set for another spell on the treatment table.
A statement released by Barca on their official website read: “Ousmane Dembele has undergone tests with the FC Barcelona Medical Services on Thursday morning and it has been confirmed that he has torn the femoral biceps muscle in his left hamstring.
“This means he will be out of action for an expected three or four weeks.
“The French striker was on for the last twenty minutes of Wednesday’s 5-1 victory over Olympique Lyonnais in the Champions League round of 16, coming off the bench to convert the last goal of a memorable night of football.
Dembele endured form and fitness issues at Barca during his debut campaign in 2017-18.
He was, however, to end that season with a place in the France squad which swept to World Cup glory in Russia.
A more regular role has been enjoyed at Camp Nou this term, with the 21-year-old taking in 35 appearances across all competitions.
He has helped to keep Barca on course for a potential treble triumph.
The Blaugrana are leading the way in La Liga as they seek to successfully defend their domestic title.
They are also through to the final of the Copa del Rey and last eight of the Champions League.
Dembele will be hoping to play a prominent role in the pursuit of those prizes, but he is now set to take in an enforced break.
The first legs of the Champions League quarter-finals are also due to take place on 9 and 10 April, which may come too soon for Dembele, with the return dates being staged a week later.