He attended primary and secondary school at Colégio Pestalozzi in his hometown, and soon moved to Rio de Janeiro.
He frequented the literary circle of Olavo Bilac, Guimarães Passos, Emílio de Meneses, Coelho Neto, Martins Fontes and others.
Much of his work was collected in the two volumes of Toda uma vida de Poetry (1957), published by José Olímpio.
In a contest promoted by the Fon-Fon magazine, in 1938, he was elected by intellectuals from all over Brazil as Prince of the Brazilian Poets, replacing Alberto de Oliveira, who had held the title since the death of Olavo Bilac.
Mariano was the third occupant of Chair 21 of the Brazilian Academy of Letters, to which he was elected on December 23, 1926, succeeding Mário de Alencar and received by Academician Gustavo Barroso on April 20, 1927.