Guarani Futebol Clube
Renato was born in Santa Mercedes, São Paulo. Known as "Renatinho" during his beginnings, he was a Guarani Futebol Clube youth graduate, and made his senior debut on 17 April 1996 when he started in a 0–1 Campeonato Paulista home loss against São Paulo FC. He scored his first professional goal on 6 September 1998, netting the first in a 2–0 home win over Sport Club Internacional.