Supporters spilled out onto the streets of the Catalan capital to see the team paraded on an open top bus sporting a banner declaring "Champions 2010-2011".
"It's a very special day with youngsters celebrating with their parents and their grandparents, a Catalan party," said Barcelona director Jordi Cardoner.
"This is a team made up of friends and when friends play well this is the result," he added.
The bus also had a sign with the words "Lorca in our hearts" in homage to the victims of this week's earthquake in southeastern Spain which left nine dead and 100 wounded.
The celebrations were set to climax with a rock concert at Barca's Camp Nou stadium.
Barcelona became the first team since 1993 to win three successive Spanish titles when they drew 1-1 at Levante on Wednesday.
Pep Guardiola's team, who were winning their 21st league title, face Manchester United in the Champions League final at Wembley on May 28.
They now have the luxury of two 'dead' league games - including Deportivo La Coruna on Sunday - to prepare for the European showpiece against United.