At the beginning of the First World War, Witzleben served as brigade adjutant in the 19th Reserve Infantry Brigade before being promoted to Hauptmann and company chief in the Reserve Infantry Regiment No.6 in October 1914. Later, in the same regiment, he became battalion commander. His unit fought in Verdun, the Champagne region and Flanders, among other places. He was seriously wounded and was awarded the Iron Cross, both first and second classes. Afterwards, he was sent to General Staff training and witnessed the war end as First General Staff Officer of the 121st Division.