Aelred was the son of the last hereditary priest of Hexham and was raised at the court of King David I of Scotland, where he became master of the household. In 1134, on a diplomatic mission to Archbishop Thurstan of York, he stopped at the newly-founded Cistercian abbey of Rievaulx, was overwhelmed by its beauty, and remained there as a novice. He served as master of novices, was made abbot of Revesby in 1143, and returned to Rievaulx as abbot in 1147.
Under his twenty-year abbacy Rievaulx grew to over 140 choir monks and 500 lay brothers, the largest single Cistercian community in England. He travelled tirelessly as a visitor for the order, wrote the Mirror of Charity (commissioned by Bernard of Clairvaux), the great dialogue On Spiritual Friendship (a Christian transformation of Cicero's De Amicitia and one of the most beloved monastic books of the Middle Ages), the Life of Edward the Confessor, sermons, and historical works.
His final years were marked by severe arthritis and kidney stones — he wrote much of his late work from a small heated cell beside the abbey infirmary. He died at Rievaulx in January 1167. The towering ruins of Rievaulx in the North York Moors remain one of the most evocative sites of English monastic history.