The 38-year-old Argentine World Cup winner, who joined Barca's youth academy at age 13 and went on to become the club's all-time top scorer with 672 goals in 778 appearances, left the Catalan side in 2021 when they could not make it financially viable to keep him.
Having won 10 LaLiga titles, four Champions League crowns and three Club World Cups with Barca, Messi now plays for Inter Miami after two years with Paris St Germain.
Barca reopened the Camp Nou on Friday, 895 days after its closure, unveiling a revamped stadium by staging an open training session attended by 21,795 fans.
"Last night, I returned to a place that I miss with all my heart. A place where I was immensely happy, where you made me feel a thousand times like the happiest person in the world," the eight-time Ballon d'Or winner wrote on Instagram on Monday.
"I hope that one day I can return, and not just to say goodbye as a player, as I never got to do."
Messi extended his contract with Inter Miami in October and has previously said that the Major League Soccer club would likely be his last.
"You're always welcome at your home, Leo," Barca posted on X.