Von Zedtwitz was born in Berlin, Germany. His mother was Mary Elizabeth Breckinridge Caldwell, daughter of American businessman William Shakespeare Caldwell, one of Louisville’s first millionaires by the late 1850s, and sister of Mary Gwendoline, Marquise des Monstiers-Mérinville. His father was Baron Moritz Curt von Zedtwitz, a German diplomat who belonged to the old Zedtwitz noble family, which rose under the Electorate of Saxony. His parents were married in June 1890. His father died in a boating accident on August 18, 1896, when he was just three months old.
He was educated at Berlin and Bern, and later served in the German cavalry during World War I. He became a naturalized American citizen.
He was a lexicographer and linguist.
Von Zedtwitz was a keen backgammon player, winning a major tournament at age 82. He lived for 47 years in New York City before relocating to Hawaii in 1977. He died in Hawaii in 1984.
He was friends with Harold Vanderbilt, the inventor of contract bridge, and became an early and enthusiastic competitor and promoter of the game, including a tour of Europe.
Von Zedtwitz was 1932 president of the American Bridge League, one of the organizations whose merger established the American Contract Bridge League (ACBL) in 1937. The ACBL credits him with saving it by his emergency service as president in 1948 and 1949. He was a founder of the World Bridge Federation.
There is an endowed Waldemar von Zedtwitz Chair at Yale university/