Tizard, who was born at Gillingham in Kent, was the son of a naval officer who served as the navigator on the Challenger voyage. Barred from a similar career by an eye accident, Tizard instead went to Oxford University where he studied chemistry under Nevil Sidgwick. After spending a year in Berlin working under Walther Nernst, he returned to Oxford in 1911 to take a fellowship. It was in Berlin that he first met and became friendly with Frederick Lindemann, who was later to become his principal opponent for positions of power in British scientific government circles.

Tizard spent World War I in the Royal Flying Corps working on the development of bomb sights and the testing of new planes. After the war he realized, as he put it in his unpublished autobiography, that he “would never be outstanding as a pure scientist.” Having developed a taste for the application of science to military problems, he took the post of assistant secretary at the Department of Scientific and Industrial Research (DSIR) in 1920 with specific responsibility for coordinating research relevant to the needs of the armed forces. In 1929, largely for financial reasons, Tizard accepted the position of rector of Imperial College, London, where he remained until 1942.

Tizard quickly established a reputation for having an expert and practical knowledge of service needs. He had the rare ability to distinguish between a crankish, totally unsound, idea and one that, though strange and new, was basically sound and could find practical military application. Thus it was that Tizard backed the young Frank Whittle in the development of jet propulsion of aircraft in 1937 and also Barnes Wallis in 1940 in his development of the bouncing bomb.

But, above all else, it was Tizard's support for the development of radar that will be remembered. In 1934 the Air Ministry set up the Committee for the Scientific Survey of Air Defence, under the chairmanship of Tizard. This was the famous ‘Tizard committee’, which, in 1935, decided that radar was a workable means of air defense and should receive top priority.

The decision was not taken without dissent. In particular, Lindemann, then Churchill's scientific adviser, while recognizing the potential of radar, did not agree with the overriding priority demanded for it by Tizard and his associates. There was a further disagreement between the two men in that Lindemann advocated mass bombing of Germany while Tizard proposed instead (in 1942) a more balanced bombing policy with adequate aircraft being committed to the Battle of the Atlantic.

As a chemist Tizard's most significant work was on the ignition of gases in the internal combustion engine. He was editor of Science of Petroleum (1938), a standard multivolume work on the subject. He was knighted in 1937.