He attended and graduated in 1952 from Columbia University and thereafter served as a high school social science teacher while working for his advanced degrees.

Prior to founding the International Association for the Advancement of Ethnology and Eugenics, he published several articles on race science and syndicalism for Oswald Mosley's The European and Corrado Gini’s Genus.

In 1960, he obtained employment as a philosophy instructor at Washington College, and in 1961 he received his doctorate at Columbia as an Irwin Edman Scholar and with Distinction in History after his dissertation on Giovanni Gentile.

Gregor was part of a movement of scholars in the 1960s who rejected the traditional interpretation of fascism as an ideologically empty, reactionary, antimodern dead end.

Gregor described fascism as a coherent and serious theory of state and society, and argued that it played a revolutionary and modernizing role in European history.

[12] Sean Kennedy in Canadian Journal of History said in 2013, "Over a long and distinguished career A. James Gregor has advanced some controversial interpretations of political ideologies.

In particular, he holds that the Italian fascist regime is best understood as a "developmental dictatorship," distinct from Nazism in key ways; a thesis that has proven surprisingly influential since 1945.

[14] Per Andreas Umland writing for The American Historical Review in 2013, "A. James Gregor has, for half a century, been one of the major makers and shapers of the discipline of comparative fascism.

[independent source needed] In the 1960s, Gregor held numerous workshops and lectures to convince policymakers and academics to be supportive of the US role in the Vietnam War.

[citation needed] Until his retirement in 2009, he taught a series of political science courses on revolutionary change, Marxism, and fascism at UC Berkeley.