Messi trains for first time since blocked attempt to leave Barca
It is not clear if Messi was training alone or with the rest of the group but the striker was taking part in his first session since Ronald Koeman was appointed coach and first since he said on Friday he had been forced to stay at Barcelona.
In an explosive interview with Goal, Messi blamed the club's president Josep Maria Bartomeu for "breaking his word" over a much-disputed exit clause in his contract.
He said he would continue to give his best for the team but maintained he had tried to leave the club because he "wanted to live his last years of football happily".
The return of Barcelona's embittered captain and greatest ever player may not be an easy one, particularly given some of his closest team-mates are likely to be absent.
Luis Suarez, Messi's best friend and neighbour, as well as Arturo Vidal, are expected to join Juventus and Inter Milan respectively.
"Now I don't know what will happen," Messi said on Friday.
"There is a new coach and new ideas. That's good, but then we have to see how the team responds and whether or not it will allow us to compete at the top level. What I can say is that I'm staying and I'm going to give my best for Barcelona."
- Long-term future in doubt -
Messi's decision to notify the club via burofax that he intended to leave came shortly after he met with Koeman, talks that reportedly involved the Dutchman taking a hard line.
Koeman said in his first press conference he "only wanted players who want to be here and give everything".
Messi also refused to attend either a coronavirus test or Koeman's first week of pre-season training last week, as his lawyers believed participating would harm his case in a potential legal battle with the club.
But Messi opted not to go down that route, insisting he could never go to court against "the club of my life".
Yet his long-term future remains in doubt given Messi can talk to other clubs in January and leave for free when his contract expires on June 30.
Messi could feature in Barcelona's friendly against Gimnastic Tarragona on Saturday but a more realistic reintroduction might be against Girona four days later.
It would be the first time he has played for the team since their historic 8-2 defeat by Bayern Munich in last month's Champions League quarter-finals.
Barcelona have been given an extra two weeks off to recover before they start their La Liga season against Villarreal, scheduled for September 27.