Born in Berlin, Germany, Cohn received his BSS in Sociology from City College (New York) in 1951.
He completed his MA (1954) and PhD (1956) at the New School for Social Research.
He joined the University of British Columbia's Department of Anthropology and Sociology in 1960 and remained there until taking early retirement in 1986.
Cohn's research focused on the sociology of Jews and small political movements, and he developed an interest in researching Romani people.
Over the years Cohn wrote numerous articles on the Romani in various scholarly journals and in 1973 he wrote The Gypsies which summarized his findings in the field.