The 34-year-old has signed a two-year deal with the option of a third at the Ligue 1 club after his 21-year stay at the Catalan outfit came to an end.
Messi’s contract, however, is reported to be worth up to £35million per year and the PSG board will now have to look at making sure they stick within financial regulations.
PSG’s other star forwards in Neymar and Kylian Mbappe will not be leaving, but reports in France and Spain suggest that players such as Ander Herrera, Idrissa Gueye, Mauro Icardi, Sergio Rico and Pablo Sarabia may be sold at cut-price deals to get them off the wage bill.
For now, though, the chat is all about Messi.
“I am very happy,” the Argentina internationalist said in his first media conference at the Parc des Princes. “You all know about my exit from Barcelona and it has been a very hard moment after so many years. It was a difficult change after so long a time.
"But the moment I arrived here I felt very happy and I really want to begin the training sessions, I want it to be quick.
"My only will now is to begin the training sessions. I want to work with the staff and team-mates and begin this new moment of my life.
"I have this will to play. I am really impatient. I still want to win.
"I feel this club is ready to fight for all the trophies. This is my goal, I want to keep growing and keep winning titles and that is why I came to this club.”
Messi admits he has considered the prospect of having to face Barcelona if PSG are drawn against them in the Champions League.
"Barcelona is my home, I have been there since I was a kid and I've lived so many things there," he continued.
"I don't know if we are going to face each other – it would be very nice to go back to Barcelona.
"It will be very strange to play at home there in Barcelona with another shirt but it can happen and we will see."
Messi also revealed that family considerations were key in his next move.
"The only thing I told Leonardo [sporting director] was I really hoped my family would be at ease in Paris and feel OK in Paris and France,” he said.
"This is new for us but I am ready in the sporting aspect. For my family it's a beautiful city so we are happy.”
We may have to wait a bit longer to see Messi in action, however, with Saturday’s Ligue 1 match against Strasbourg likely to come too soon for him.
"Actually, I don't know,” he responded when asked when his first game will be. "I spoke yesterday with the technical staff, so, maybe I need a pre-season.
"I'm going to begin to train and work and I hope I can play as soon as I can, when the staff thinks I'm OK, I'll be ready."