The Argentine Ballon d'Or nominee was suffering from a hamstring injury and has not featured for the Catalan club since a 4-1 victory over Real Betis on November 10, but returned from his homeland to resume training last week.
And Barca coach Gerardo Martino has named the forward in his 18-man squad to take on Getafe in the last 16 of the Copa del Rey on Wednesday.
"Leo feels good," said Martino. "He has been training well, and he's ready to play now. We're all happy he's back.
"We will decide tomorrow if Messi starts the game or not.
"He does bring an air of confidence into the team. Not just football, but in terms of morale."
However, the Spanish champions will be without Marc Bartra, Xavi and Daniel Alves for the first-leg encounter.
"Bartra had some discomfort last game," added Martino. "He's fine, but my instinct tells me not to take any risks. Same for Xavi.
"Alves has just recovered from flu, he needs some more training to be fully fit."
The omission of Xavi and Bartra may suggest Martino has one eye on Saturday's top-of-the-table clash with Atletico Madrid, but the coach insisted his charges are fully focused on the club's cup campaign.
"The players won't have their mind at all on Saturday," he stressed. "We have a big game tomorrow and there is no room for error in a cup tournament.
"We've got our minds strictly on tomorrow's game. It's important to make sure the players don't get distracted by things around them."
