Keitel was born in Bad Gandersheim,

Keitel was born in Bad Gandersheim, Duchy of Brunswick, German Empire, the son of Carl Keitel, a middle class landowner and his wife Apollonia Vissering. After completing his education in Göttingen, he embarked on a military career in 1901, becoming a Fahnenjunker (Cadet Officer), joining the 6th Lower-Saxon Field Artillery Regiment. He married Lisa Fontaine, a wealthy landowner's daughter, in 1909. Together they had six children, one of whom died in infancy. His eldest son, Karl-Heinz Keitel went on to serve as a divisional commander in the Waffen-SS. During World War I Keitel served on the Western Front with Field Artillery Regiment No. 46. In September 1914, during the fighting in Flanders, he was severely wounded in his right forearm by a shell fragment. Keitel recovered, and thereafter was posted to the German General Staff in early 1915. After World War I ended, he stayed in the newly created Reichswehr, and played a part in organising Freikorps frontier guard units on the Polish border. Keitel also served as a divisional general staff officer, and later taught at the Hanover Cavalry School for two years.
In late 1924, Keitel was transferred to the Ministry of Defence (Reichswehrministerium), serving with the Troop Office (Truppenamt), the post-Versailles disguised General Staff. He was soon promoted to the head of the organisational department, a post he retained after the Nazi seizure of power in 1933. He suffered a heart attack and double pneumonia in the autumn of 1932. In 1935, based on a recommendation by Werner von Fritsch, Keitel was promoted to major-general and appointed as the departmental head of the Wehrmachtsamt (Armed Forces Office) which had the responsibility over all three branches of the armed forces.