Selton Mello began his career in voice acting during the 1980s and 1990s, a period in which he was a prolific dublador for the Brazilian Portuguese versions of various films and television series. This early phase of his career was marked by a formal employment relationship with a dubbing studio. It was during this time that he voiced the character Nick, one of the two toupeira brothers, in the Japanese anime series Nick & Neck (titled Dorimogu Daa! in Japan), which aired in Brazil in the early 1990s. The dubbing for this series was produced by the renowned Herbert Richers studio in Rio de Janeiro.

His voice acting work from this period includes a range of iconic characters. He provided the Brazilian voice for Daniel San in The Karate Kid Part II and The Karate Kid Part III, John Bender in The Breakfast Club, and the character Jones in the Police Academy films. He also dubbed characters for television, such as Harry Truman Loki in, and the young Indiana Jones in Indiana Jones and the Last Crusade. Additionally, he was the voice of Charlie Brown in the Peanuts cartoons broadcast by TV Globo during the 1980s and 1990s. His credits from this era also include the character Daniel Witwicky for a VHS release of The Transformers: The Movie.

Following this initial prolific period, Mello's approach to dubbing became more selective, taking on roles as a guest voice actor rather than as a regular studio employee. In 2000, he voiced the character Kuzco in the Brazilian Portuguese dub of the Disney animated feature The Emperor's New Groove. He continued to lend his voice to animated films in the ensuing years, including a role in the 2003 Brazilian dub of Brother Bear. In 2013, he voiced the character of the Immortal Warrior in the Brazilian animated film Rio 2096: A Story of Love and Fury. More recently, in 2017, he took on the title role of Lino in the Brazilian animated feature Lino: O Filme – uma aventura de sete vidas.