Harvey was born in the English coastal town of Folkestone and educated at King's School, Canterbury, and Cambridge University. In 1599 he made the then customary visit to Italy where he studied medicine at the University of Padua under the anatomist Fabricius ab Aquapendente, obtaining his MD in 1602. He was appointed physician at St. Bartholomew's Hospital, London, in 1609 and in 1618 began working at the court as physician extraordinary to James I. He also served Charles I, accompanying him on his various travels and campaigns throughout the English Civil War. He was rewarded briefly with the office of warden of Merton College, Oxford, in 1645 but with the surrender of Oxford to the Puritans in 1646 Harvey, suffering much from gout, took the opportunity to retire into private life.

In 1628 Harvey published De motu cordis et sanguinis in animalibus (On the Motion of the Heart and Blood in Animals). This announced the single most important discovery of the modern period in anatomy and physiology, namely, the circulation of the blood. The orthodox view, going back to Galen, saw blood originating in the liver and from there being distributed throughout the body. There was no circulation for Galen and he believed that the arteries and veins carried different substances. Harvey made a simple calculation that revealed the prodigious amounts of blood that would have to be produced if there was no circulation. Harvey also could not understand why the valves in the veins were placed so that they allowed free movement of blood to the heart but not away from it. It did however make sense if blood was pumped to the limbs through the arteries and returned through the veins.

Harvey then set about demonstrating his supposition. He examined the action of the heart of such cold-blooded creatures as frogs, snakes, and fishes as their slower heart rate allows clearer observations to be made. This enabled him to establish that blood passes from the right to the left side of the heart not through the wall, or septum, which was solid, but via the lungs. It was also clear that blood is pumped from the heart into the arteries, for he observed that they begin to fill at the moment when the heart contracts. Between contractions, the heart fills with blood from the veins. The heart is thus, Harvey declared, nothing more than a pump. To show that blood passes from the arteries to the veins rather than vice versa, Harvey resorted to a number of simple and compelling experiments with ligatures.

Harvey's 72-page masterpiece received considerable but by no means universal support. There was, as he was well aware, one weak link in his argument, namely the precise connection, or anastomoses, between the arterial and venous system. He thus had to accept, without observation, that the hair-thin capillaries of the two systems did in fact link up. Harvey only had a magnifying glass at his disposal and it was left to Marcello Malpighi to observe the implied anastomoses through his microscope in 1661. The importance of Harvey's discovery lay in providing an alternative to the Galenic theory, thus encouraging other scientists to question the authority of ancient texts.

Harvey also worked in embryology. He argued that all life arose from the egg thus denying spontaneous generation. To describe the process of generation he thought he had observed in chickens and deer, Harvey coined the term epigenesis. By this he meant the female egg possessed an independent existence and was capable of completing its development through the activity of its own vital principle. It did not join with the semen, nor was it fertilized by it. Harvey believed the semen acted by initiating the self-contained development of the egg through touch alone. However with the increasing use of the microscope and the earlier identification of anatomical features within the egg by Malpighi in 1673 the alternative preformationist view began to gain ground.

Harvey became a figure of much influence within the College of Physicians. He served as treasurer in 1628 and although offered the presidency in 1654 felt compelled to decline it on grounds of health.