Kay Fisker was born on 14 February 1893 in the Frederiksberg, Copenhagen. He entered the Royal Danish Academy of Fine Arts in 1898 and while there worked at the offices of leading Scandinavian architects such as Anthon Rosen, Sigurd Lewerentz, Gunnar Asplund and Hack Kampmann parallel to his studies. In 1915, in collaboration with Aage Rafn, he won a competition to design the railway stations along the Almindingen - Gudhjem railway on the Danish island of Bornholm.

After graduating, his career as a practicing architect was dominated by numerous influential residential projects. Vestersøhus was built in from 1935 to 1939 by Fisker and C.F. Møller. It instantly became a model in Denmark for the balcony and bay window blocks of the time.

A key building in his production was Århus University (1932 – 43), considered to be one of the most important examples of Danish Functionalism, which he designed in collaboration with Povl Stegmann and later C.F. Møller, and with Carl Theodor Marius Sørensen. Kay Fisker also designed the Danish Academy in Rome.

From 1936 to 1963 Fisker was a professor at the Royal Academy and as teacher of the school's class on housing he was known as an inspiring lecturer with great influence on Danish housing culture. From 1951 to 1957 he was a visiting professor at the Massachusetts Institute of Technology.