Horacio Serpa worked in three branches of government in Colombia. After graduating as a lawyer from the "Universidad del Atlántico" in Barranquilla, Serpa went back to his native Santander Department and became a judge for the town of Tona. He later became a Penal Judge in the town of San Vicente de Chucurí and then Civil Municipal Judge in Barrancabermeja. In Barrancabermeja Serpa also served as Criminal Investigator, Circuit Penal Judge and Superior Judge. During this time Serpa became interested in politics and began participating actively in the Liberal Revolutionary Movement (MRL) as member of the youths, this movement had been founded by Alfonso López Michelsen.