A jubilant Nou Camp crowd responded by celebrating a remarkable eighth league crown in 11 years.
Barca’s captain decided the game and the title in the 61st minute as he received a header from Arturo Vidal, effortlessly freeing himself from two defenders with his right foot.
He then used his left foot to plant the ball into the far bottom corner.
Cries of “champions” rang out from the 91,000 supporters crammed into the Nou Camp but Barca’s players dropped their concentration and Jose Luis Morales should have levelled for the visitors.
But he blasted over the bar.
Levante also hit the post in the final stages as Barca were left clinging on to their narrow advantage deep into stoppage-time.
But relief came when they cleared a corner kick and the final whistle sounded.
Barca lead the standings on 83 points after 35 games, an unassailable nine clear of second-placed Atletico Madrid with three matches left.
That was because they have a superior head-to-head record with Atletico Madrid this season.
Ernesto Valverde’s side have now taken the first step in their bid to win a third treble in a decade.