Cowell was educated at Ardingly College before entering Trinity College, Cambridge where he completed his BA (1971), MA (1975) and PhD (1977) in Economics. Cowell was briefly Lecturer in Economics at University of Keele before moving to LSE in 1977. He was also Associate Editor of the Journal of Public Economics from 1988-2001.

Cowell is the former editor of Economica, and the editor-in-chief of the Journal of Economic Inequality. He is also the Director of Distributional Analysis Research Programme at the Suntory-Toyota International Centre for Economics and Related Disciplines.

He has an h-index of 52 according to Google Scholar.

His work includes important contributions to the fields of income and wealth distribution, inequality, poverty and taxation.