Four Quartets (1942) is a sequence of four poems: 'Burnt Norton' (1936), 'East Coker' (1940), 'The Dry Salvages' (1941) and 'Little Gidding' (1942). The main sources of the mystical symbols in T.S. Eliot's masterpiece, Four Quartets, are some of Saint John of the Cross's writings and this has not been given its due of study. This paper aims at exploring St. John of the Cross's influence on Eliot's Four Quartets, especially his Dark Night of the Soul and The Ascent of Mount Carmel. The downward movement, the descent into the inner darkness and the symbols of ascending and descending of the stairs in Eliot's poems were among the outstanding mystical symbols used by John of the Cross. Eliot also strongly echoes John of the Cross in his emphases that one must die to self and undergo mortification of the body before one can hope for the perfect union of the soul with God. The paper attempts to investigate Eliot's use of these and other symbols relating them to their counterparts in the works of St. John of the Cross.