On February 14, 1968, Carberry was appointed the fifth Archbishop of St. Louis, Missouri. His installation took place at the Cathedral of St. Louis on March 25 of that year. Carberry was considered more theologically conservative than his predecessor, Cardinal Joseph Ritter. One publication even described him as being "threatened by a world he does not understand." He strongly defended "Humanae vitae", and created the Archdiocesan Pro-Life Commission. Paul VI created him Cardinal Priest of "S. Giovanni Battista de Rossi a via Latina" in the consistory of April 28, 1969. In 1969 he removed about 60 of his seminarians from a class at the Saint Louis University Divinity School, in objection to their being taught Pauls' epistles by the Presbyterian scholar Keith Nickle.