[citation needed] At the age of 18, Villablanca started his career as a professional boxer, when he defeated Luis Conejeros by a decision in four rounds, on January 23, 1976, in Santiago.
[citation needed] On January 20, 1979, Villablanca had his first fight as a professional abroad, when he faced Victor Etchegaray for the South American Jr. Lightweight championship in Bariloche, Argentina.
[citation needed] Back in Chile, Villablanca retained his Chilean Jr. Lightweight title with a victory over Diaz in a rematch, on March 3, 1979, by knockout in the eighth round.
[citation needed] Villablanca then embarked in an eleven fight winning streak, which included a twelve-round decision over Luis Bendezu on August 7, 1981, which made him the WBA's Fedelatin Jr. Lightweight champion.
[citation needed] On June 5 in Santiago, four months after his victory over Julio Hernandez, Villablanca challenged Serrano, for the WBA's world Jr. Lightweight title.
When the fight was stopped in round eleven due to Serrano's cut, Villablanca was declared winner, and new WBA world Jr. Lightweight champion, by an eleventh-round knockout.
[citation needed] After the disappointment of seeing his world champion status disappear, Villablanca returned to professional boxing with three consecutive victories, including a ten-round decision over Geronimo Luque.
[citation needed] Villablanca won his next four bouts, but, after losing on December 20, 1985 to Ricardo Toledo by a knockout in three rounds in Santiago, he retired from professional boxing for good.