During the 1960s, in the early phases of the military dictatorship in Brazil, he was charged by the press with belonging to a paramilitary right-wing organization, Commando for Communist Hunting (Comando de Caça aos Comunistas, CCC) which was aimed at harassing and bullying leftist students.

[2] From 1974 to 1984, Casoy worked in the Paulista newspaper, Folha de S.Paulo - firstly as chief editor, a position in which he had to share power with the redaction director, the Trotskyist sympathizer Cláudio Abramo.

As anchor, Casoy became famous for his rhetorical outbursts, as he acquired the habit of expressing disagreement with unpleasant facts (mainly corruption scandals) he had described by uttering repeatedly: "For shame!"

However, he had speculated that there was pressure from the Worker's Party, since he and his crew were unrelenting in investigating and exposing alleged scandals and corruption cases in the left-wing government.

On April 14, 2008, Boris Casoy returned to national television on Rede Bandeirantes as the main anchor for its nightly newscast, Jornal da Noite.