Romero began training in Brazilian Jiu Jitsu at age 11. He was nicknamed Jacaré because he used to wear Lacoste polo shirts in his youth.
By the age of 16, Romero regularly attended jiu jitsu classes at the famous Gracie School in Copacabana where he grew up, alongside Carlos Gracie, Jr., Crolin Gracie, Mario Claudio Tallarico, Fábio Santos, Mauricio Motta Gomes, the Machados, and Rickson Gracie.[1][2] After extensive competition from 1972 to 1985 and working as an assistant instructor at the Gracie school, Romero opened his first school in Ipanema, Brazil. Romero had studied in New York in the 1970s, and in 1995 he moved back to the US with his family and opened a Brazilian Jiu Jitsu school in Miami. He later moved to Atlanta where he established a school in late 1996.[4]