Wilhelm Veller, known as Willi, was born in Witten, Province of Westphalia as the son of an independent businessman. After attending Volksschule and the Oberrealschule, he enlisted and fought at the beginning of World War I. He was wounded three times and promoted to sergeant. He was named an officer candidate in 1915. In 1916, became a prisoner of war in Russia, where he was held in prison in Siberia. He was able to flee after the Russian Revolution and return to Germany, where he returned to his old regiment. While on leave, he enrolled at the University of Bonn, where he later received a doctorate in philosophy. In August 1918, he joined the replacement pilots division in Altenburg. After the war, Veller returned home and worked in his father's business, taking it over in 1928, after his father died. He went bankrupt in 1930.
