The triumph sums up the club’s domestic dominance, representing their third straight league title and their sixth in the last eight seasons.
Al Sadd sealed the title as Al Shamal lost 2-0 to Qatar SC with one matchday to go, now holding an unassailable five-point lead.
Brazilian international Firmino was superb all season, finishing the campaign with 16 goal contributions in 20 league matches.
He was not alone in driving Al Sadd’s success. Akram Afif also demonstrated his importance to the side with influential displays across the season, registering 14 league goals and 12 assists, while Rafa Mujica also emerged as a crucial figure, scoring nine goals.