The 34-year-old left Barcelona as a free agent with the LaLiga side unable to offer him a new contract due to financial difficulties. Messi was officially unveiled as a PSG player on Tuesday, signing a two-year contract, with the option of a third.
Messi's former Barca team-mate Ronaldinho - who also played for PSG - believes the French giants can finally clinch the coveted Champions League trophy this season.
"It's a great joy to have played in these two clubs and now see my friend wearing this shirt, may there be many moments of joy Leo!!!" he wrote on Twitter. "I'm also very happy with my partner @SergioRamos on the team and a super cast, I'm smelling Champions huh hahaha."
Messi was pictured holding a No 30 shirt upon his unveiling and the club announced they have already sold out of their home shirts with the name and number on the back. TV pundit and Arsenal fan Piers Morgan claimed that the club will recoup Messi's mammoth £25-30million per season salary through shirt sales.
"PSG will get their Messi money back in shirt sales in six months. Great business," he tweeted.
The 34-year-old admitted he is excited to get started with PSG, and said: "I am excited to begin a new chapter of my career at Paris Saint-Germain. Everything about the club matches my football ambitions. I am determined to help build something special for the club and the fans."