In 1945 he remarried to Elisabeth Margareta Heurlin (1919-1968). Fifteen years after Elisabeth's death, he married a third time, to Karin Lindén (1931-1996). It was unusual that one so young as Giertz (43) would be elected bishop. Until his election he had been just an assistant vicar of a small rural parish. Previous bishops had usually been head priests of large parishes or university theologians. During his time as bishop (1949–1970) he did not write many major works. As custom dictated, he wrote a "Herdabrev" (pastoral letter) that outlined his theological program. This “letter” was really a book-length text, in which he outlined the inheritance of the Church of Sweden from three different eras — the first being the early church or New Testament times, the second being the Reformation, and a third on 19th-century revival. In a chapter of this work with the English title “Liturgy and Spiritual Awakening”, he makes a case for the necessity of ancient liturgy in the life of the church. The work shows the importance Giertz put upon the word of God in scripture, sacraments and prayer. As bishop, Giertz's service for Lutheranism in Sweden included working with unions, touring the parishes for which he was responsible, and ordaining other priests and bishops. Abroad, he represented the Church of Sweden as second vice-president of the Lutheran World Federation. But Giertz was undoubtedly best known for his controversial stridency against the ordination of women. In 1958 the Church of Sweden voted to begin ordaining women; in strong disagreement with the modern consensus, Giertz responded immediately by organizing the group "Kyrklig samling kring bibeln och bekännelsen" ("Church coalition for the Bible and confession") and writing numerous articles defending his views in journals and newspapers. After his official retirement as bishop in 1970, Giertz returned to the task of writing. His published works from this time of his life included "Riddarna på Rhodos" ("The Knights of Rhodes", 1972), a novel exploring the theology of the cross amidst the siege of Rhodes in 1522 and a two-volume devotional work, "Att tro på Kristus" and "Att leva med Kristus", published in English as “To Live With Christ.”