On Tuesday, the 34-year-old signed a two-year deal with PSG with the option of an additional year.
Messi, who will wear the No 30 in Paris, the number he had when he began his professional career at Barcelona, will be unveiled by PSG at a press conference at 9am GMT (1pm in UAE) on Wednesday.
"I am excited to begin a new chapter of my career at Paris Saint-Germain," he said in a statement on the club's website.
"Everything about the club matches my football ambitions," Messi, who was given a hero's welcome by the PSG fans when he arrived in the French capital on Tuesday, added.
"I know how talented the squad and the coaching staff are here.
"I am determined to help build something special for the club and the fans, and I am looking forward to stepping out onto the pitch at the Parc des Princes."