Lúcia moved to Oporto in 1921, and at 14 was admitted as a boarder in the school of the Sisters of St. Dorothy in Vilar, on the city’s outskirts.
On October 24, 1925, she entered the Institute of the Sisters of St. Dorothy as a postulant in the convent in Tuy, Spain, just across the northern Portuguese border.
Lúcia made her first vows on October 3, 1928, and her perpetual vows on October 3, 1934, receiving the name Sister Maria das Dores (Mary of the Sorrows).
She returned to Portugal in 1946 (where she visited Fatima incognito) and in March 1948 after receiving special papal permission to be relieved of her perpetual vows, entered the Carmelite convent of St. Teresa in Coimbra, where she resided until her death. She made her profession as a Discalced Carmelite on May 31, 1949, taking the name Sister Maria Lúcia of Jesus and the Immaculate Heart.