The 34-year-old's new contract with the Parisians is subject to a medical and has the option of another one year.
Messi had the intentions of staying with Barcelona but the club failed to afford a new deal under La Liga's financial fair play rules.
With Messi set to complete his move to the Parc de Princes, a news conference is expected to come off on Wednesday at 10:00 BST.
Confirming the Argentine's shocking move to PSG, Guillem Balague said;
"It's all been confirmed. Lionel Messi is going to be a PSG player," Balague said on BBC Radio 5 Live. "That's it, it's done. It's happened in the last few minutes.
"At the moment there are as much police as there are fans [at the stadium]. That's going to change soon.
There's eight cameras here, again that's going to change. It seems like it is a two-year deal, plus one.
"His idea was to do it at Barcelona but it's going to be PSG. Then if he feels OK he will stay one more year maybe. But in any case his aim is to be at PSG and then to do well in the Qatar World Cup."
The six-time Ballon d'Or winner was pictured with his family at Barcelona's El Prat airport on Tuesday afternoon as they head to Paris to finalise his move to the French Ligue 1 giants.
And confirming the deal to reporters Messi's father Jorge Messi answered "yes" When asked by reporters whether his son would be joining PSG.
