Born in the Pernambuco state capital Recife, Filho moved to Rio de Janeiro while still a child, in 1916.

The younger Mário began at his father's paper in 1926 as a sports reporter, pursuing a relatively undeveloped form of journalism.

Mário Filho began his career as a reporter for the daily newspaper A Manhã in Rio, which was then in possession of his father.

Filho was himself an ardent follower of football, which had established itself in Brazil since the turn of the century, and filled with reporting on all sides, which was uncommon in those days.

The myth of the derbies phase between the leading football teams of Rio Fluminense and Flamengo is also attributed to him, to be co-founded.

Its main adversary was the journalist and councilor Carlos Lacerda, later aspirant for president and governor of the state of Guanabara.

As early as the 1950s, he let the readers of Journal dos Sports know, that his heart beat for Fluminense The great playwright and chronicler Nelson Rodrigues, brother of Mario Filho, honored him with the name "o criador das multidões", "the creator of crowds".