Jaroslav Fragner started to study after World War I, but did not graduated. He began to work at Karel Honzík's and Evžen Linhart's offices. From the year 1922 he started his own business. He probably felt the need for a degree, so he finished architecture at Josef Gočár's Academy in 1934 and 1935.
He started with Cubistic works, than followed the international Modernism. He was active in Prague and in the area around Kolín. During the 1930s he started to use more neoclassical elements.
As a left-wing architect he joined the group of Devětsil. After the group's break-up in 1931 he became active in the Artist's Association Mánes, trying to connect Czech artists with international famous artists.
During the communist regimme in Czechoslovakia he did not succeed to stop the state in nationalizing the association. Because of his protests he was banned as an architect in 1959, but in 1965 he was contradictorily named National artist.