Doolittle was educated at Los Angeles Junior College (1914–16) and the University of California School of Mines (1916–17). As an army enlistee during World War I, he became an expert aviator and flight instructor. He stayed in the Army Air Corps after the war, was promoted to first lieutenant in 1920, and also studied at the Massachusetts Institute of Technology (Cambridge, Mass.), where in 1925 he received a doctorate in advanced engineering.

Doolittle remained in the Army Air Corps until 1930, demonstrating, testing, and racing aircraft. Upon resigning his commission, he took charge of the aviation department of the Shell Oil Company. While serving as a consultant to the government and the military, he continued to race aircraft, setting a world high-speed record in 1932.

With the outbreak of World War II, Doolittle returned to active duty in the Army Air Forces. On April 18, 1942, he commanded a bombing mission that began on the deck of the aircraft carrier Hornet. Sixteen B-25s struck Tokyo, Yokohama, and other Japanese cities. The planes then proceeded westward, and most of the crews arrived safely behind friendly lines on the Chinese mainland. While the raid did little damage, it greatly bolstered U.S. morale and caused the Japanese to shift precious resources to air defense.

Doolittle, made a brigadier general after the raid, received the Congressional Medal of Honor for his actions and soon was promoted to major general. He continued to lead air operations during the war, on the European, North African, and Pacific fronts, winning promotion to lieutenant general in 1944. He commanded the 8th Air Force in its attacks on Germany during 1944–45. After the war he returned to Shell Oil and to advisory positions in both the public and private sectors, remaining active in the aerospace industry after retiring in 1959. He received the Presidential Medal of Freedom in 1989.