The Argentine has missed Barca's last three matches against Real Mallorca, Real Zaragoza and Levante because of a hamstring injury.
However, despite reports that he may miss out again tonight, a statement on the club's official website earlier this evening has revealed that the 25-year-old is available for selection.
"Leo Messi was given the medical all-clear this Tuesday afternoon ahead of the away leg of the Champions League semi-final against Bayern Munich," read the statement. "Messi, who was injured in the Champions League quarter-finals against Paris Saint-Germain, has totally recovered from the hamstring injury he picked up in France."
Messi has scored eight goals in the Champions League this season.