One of Hahn's main abiding concerns was the understanding of Keynesian (Non-Walrasian) outcomes in general equilibrium situations.

Frank's older brother was Peter Hahn (8 November 1923 – 28 August 2007) who became an eminent Czech research physiologist who had returned to Czechoslovakia after the War but was compelled to flee to Canada after the Prague Spring in 1968 in which he was active.

[3] Frank Hahn took his doctoral degree in 1951 at the London School of Economics (LSE) for the thesis The share of wages: an enquiry into the theory of distribution, where he was supervised initially by Nicholas Kaldor and later by Lionel Robbins.

[4] He gained widespread recognition and attention in 1981 as the co-instigator of a letter to The Times signed by 364 of Britain's best-known economists, questioning Margaret Thatcher's economic policy, with a warning that it would only result in deepening the prevailing depression.

Frank Hahn, by his own admission, was influenced in economics by John Hicks, W. M. Gorman, Takashi Negishi and Kenneth Arrow among others.