In the 1970s Balzerani became a leader of the Red Brigades (Italian "Brigate Rosse", or BR, which she had joined in 1975) in Rome. She took part in several killings, such as that of Girolamo Minervini and the assassination of Aldo Moro's escort in Via Fani (1978). After the arrest of BR's national leader Mario Moretti in 1981, she unsuccessfully tried to handle the split in the organization, becoming a leader of the "Brigate Rosse - Partito Comunista Combattente", while Giovanni Senzani led the other faction, the "BR - Partito Guerriglia".