In May 1941, he experienced the sinking of the battleship Bismarck as fourth artillery officer with the rank of lieutenant commander, thereby becoming the highest-ranking survivor of the ship.

[2] He was rescued by the British cruiser Dorsetshire and, after initial detention in England, was transported to Canada to the Bowmanville POW camp in Bowmanville, Ontario, from early April 1942 until it closed in April 1945.

In 1965, he became the West German ambassador to the Democratic Republic of the Congo during the tenure of Moïse Tshombe as a prime minister.

von Müllenheim-Rechberg would later write a book about Tshombe's kidnapping by Francis Bodenan in 1967 and his death during his imprisonment in Algeria in 1969.

That same year, he received the Grand Cross 1st Class of the Federal Republic of Germany.