Following the war, he pursued a calling to the priesthood and was ordained in 1949. He served as a priest within the Munich archdiocese. He was instrumental in the hosting of the 37th Eucharistic Congress in Munich in 1960. In 1962, he was appointed by Julius Cardinal Döpfner as Vicar-general of the archdiocese. He attended the Second Vatican Council as an assistant to Cardinal Döpfner.
In 1968 he was appointed by Paul VI as auxiliary bishop of Munich and Freising. He took the motto 'Servant of All' (Omnium Servus). He was known to give reunion masses for his former comrades in the 114th division. On one occasion he preached, "What the dust of the Russian steppes, the fields of the Caucasus, what the bursting of the grenades have wrought ... will withstand the pragmatic materialism of our time".[2]
In 1969, however, the atrocity his unit committed in Italy came to light when it was published by the German Der Spiegel newspaper. Der Spiegel also reported that the Frankfurt Crime Department had also investigated Defregger on suspicion of wartime murder the previous year. Dietrich Rahn, Frankfurt's chief prosecutor, claimed that Defregger may have been guilty of manslaughter for his role in carrying out the atrocity, however, the German statute of limitations for manslaughter had already passed by that point. Cardinal Döpfner shocked many Catholics when he admitted that he had always known about Defregger's past, but he defended him, alleging that Defregger had tried to resist the order and that failing to carry it out would have meant his own execution.[3]
Legal proceedings were carried out against him in 1969 and 1970, but ultimately dropped.[4] In 1981, an assassination attempt was made on him.
He retired in 1990, but continued to preach up to his death in 1995.
