The Argentina star has hailed the impact the former Blaugrana man had on him at the start of his career
The four-time Ballon d'Or winner made his Blaugrana debut back in 2004, a year after the Brazilian joined the club from Paris Saint-Germain and set about becoming a Camp Nou idol.
It is a time Messi has never forgotten and he admits the welcoming presence of Ronaldinho ensured his transition to the first team was a smooth one.
He told Barca TV: I've always said, since the first moment I walked in the locker room, Ronaldinho and other Brazilians, Deco, Sylvinho and [Thiago] Motta welcomed me and provided me things, but mostly he (Ronaldinho), and I learned a lot at his side."
"It was a big help. It's never easy to go into a locker room as a teenager and Ronaldinho made everything easier. I was fortunate to live near him and share many things with him. I can say that he is a great person and that's the most important thing."
Ronaldinho lifted two Liga titles and the Champions League during a five-year spell at Camp Nou and Messi believes the 33-year-old was the biggest sole influence behind that side's success.
He continued: "Ronaldinho was responsible for changing the club. The club was going through a bad spell but it changed with his arrival.
"During the first year we did not win anything but people loved him. Later came the titles and he made all those people happy. I believe that Barca should be forever grateful for everything he did."
The Brazil international eventually left the club for AC Milan in 2008, before joining Flamengo and then Atletico Mineiro in 2012.