Barca would have tied up the league title regardless of the Blancos' result in Catalunya by beating Atletico Madrid a day later, but their arch-rivals could only muster a 1-1 draw - thus handing FCB the championship without kicking a ball.
Speaking via his profile on the Chinese social networking site Tencent Weibo, the Argentine forward wrote: "After a great year's work I'm happy to celebrate the title! Congratulations to my team-mates!"
Meanwhile, Messi's colleagues Dani Alves and Cesc Fabregas took to Twitter to air their jubilation with Barca's Liga success.
The former Sevilla man posted a picture of coach Tito Vilanova and fellow defender Eric Abidal - both of whom returned to football after successfully battling cancer, and added: "Congratulations to all my colleagues for the championship, especially those in the photo! This is for you Tito and Abi."Fabregas, meanwhile, tweeted: "Today is a great day, the result of a brilliant season! I am really happy I can celebrate my first Liga title! #ForcaBarca #LigaBBVA."
And last but not least, it was a day to remember for Andres Iniesta who also celebrated his 29th birthday, and the midfielder rather fittingly posted a picture of himself with a cake, before writing: "The best gift, turned 29 and won the league... The reward for the work of the whole year!!"