Jose Mourinho's side needed to win to keep alive their slim hopes of a second successive title but were held at Cornella-El Prat.
The result leaves Tito Vilanova's side seven points clear of their fierce rivals, with Madrid only having two games left to play.
The triumph is the Catalan giants' 22nd league title and the fourth time in five years the club have topped the division.
Barca play Atletico Madrid tomorrow evening at the Vicente Calderon and have two matches in hand over Madrid.
Los Blancos will contest the Copa del Rey final against their local rivals Atletico on May 17.