On December 19, 1935, Câmara was appointed the first Bishop of Mossoró by Pope Pius XI. He received his episcopal consecration on February 2, 1936, from Archbishop Domingues de Oliveira, with Bishops Pio de Freitas Silveira, CM, and Daniel Hostin, OFM, serving as co-consecrators. Câmara was later named Archbishop of Belém do Pará on September 15, 1941, and Archbishop of São Sebastião do Rio de Janeiro on July 3, 1943.
Pope Pius XII created him Cardinal Priest of Santi Bonifacio ed Alessio in the consistory of February 18, 1946. Câmara was made the first Bishop of the Catholic Military Ordinariate of Brazil on November 6, 1950 (a post which he resigned on November 9, 1963), and the first Ordinary for the Eastern Catholics in Brazil on November 14, 1951. The Cardinal attended the first general conference of the Latin American Episcopal Conference in 1955, served as President of the Brazilian Episcopal Conference from 1958 to 1963, and was one of the participated in the conclave of 1958. From 1962 to 1965, he attended the Second Vatican Council, during the course of which he served as a cardinal elector in the 1963 papal conclave that selected Pope Paul VI. Along with Lawrence Cardinal Shehan, he assisted Leo Cardinal Suenens in delivering one of the closing messages of the Council on December 8, 1965.