He was a liberation theologian and the founder of the primitivist art community in the Solentiname Islands, where he lived for more than ten years (1965–1977).

A first cousin of the poet Pablo Antonio Cuadra, Cardenal studied literature in Managua and then from 1942 to 1946 in Mexico and from 1947 to 1949 in New York City.

After a deep mystical experience that Cardenal had on June,2, 1956,[2] in 1957 he entered the Trappist Monastery of Gethsemani (Kentucky, United States), joining another poet-priest, Thomas Merton, who was the master of novices; but in 1959, he left to study theology in Cuernavaca, Mexico.

The colony engaged with painting as well as sculpture and was visited many times by artists and writers of the region such as Willarson Brandt, Julio Cortázar, Asilia Guillén, and Aedes Margarita.

Many members of the Solentiname community engaged in the revolutionary process through guerrilla warfare that the FSLN had developed to strike at the regime.

When Pope John Paul II visited Nicaragua in 1983, he openly scolded Ernesto Cardenal, who knelt before him on the Managua airport runway, for resisting his order to resign from the government, and admonished him: "Usted tiene que arreglar sus asuntos con la Iglesia" ("You must fix your affairs with the Church").

During a short visit to India, he made a profound impression on a group of writers called the Hungry Generation.

Cardenal's tour of the United States in 2011 to promote his newest work stirred up some controversy, as with the American Society for the Defense of Tradition, Family and Property that protested his appearances at Catholic schools such as Xavier University in Cincinnati, Ohio, because of his Marxist ideology.

[11] His return to ministry was also confirmed by Managua Auxiliary Bishop Silvio Báez, who stated “I visited my friend priest, Father Ernesto Cardenal, in the hospital, with whom I could talk for a few minutes.

[14][15] His funeral was held in the Managua Cathedral on March 3, 2020, and was disrupted by at least 100 pro-Ortega protestors who shouted "viva Daniel" and "traitor" at his Nicaraguan flag-draped casket.

Some of his latest works are heavily influenced by his understanding of science and evolution, though it is still in dialogue with his earlier Marxist and Catholic material.

[23] Cardenal sums up his later material in a PBS NewsHour interview: In the first place, one matures, and can write about things one couldn't before.