The 47-year-old played for both Barca and their Spanish bitter rivals Real Madrid in the 1990s and was successful with both teams.
Hagi, himself regarded as one of the best players of all time, says that at the moment Messi is better than Real Madrid forward Cristiano Ronaldo.
"Cristiano Ronaldo is very good, but I prefer Messi," Hagi told reporters.
"He's amazing, not only for what he does on the field but also because he is a role model and, in these times, that is very important for children."
Barcelona will continue their pre-season preparations with a friendly game against Dinamo Bucharest on Saturday.