He was at the 1979 Pan American Games, in San Juan. He won a silver medal in the 4×200-metre freestyle, and a bronze medal in the 4×100-metre freestyle.[4] He also finished 7th in the 200-metre freestyle, and 13th in the 100-metre freestyle. He broke the South American record of the 4×200-metre freestyle.[5]
Mattioli won the bronze medal in the men's 4×200-metre freestyle relay event at the 1980 Summer Olympics, alongside Jorge Fernandes, Cyro Delgado, and Djan Madruga, with a time of 7:29.30. He also swam the 100-metre butterfly, 200-metre butterfly and 200-metre freestyle, not going to the final.[6]