He attended Harvard University, earning a B.A. in 1926, and an M.A. in 1927. He was on a successful track in the publishing business, when the beginning of the Great Depression radicalized him. He joined the Trotskyist Communist League of America in 1933 and was a member of the National Committee of the Socialist Workers Party (SWP) from 1940 to 1973.
In 1937-40 Novack served as the secretary of the American Committee for the Defence of Leon Trotsky. This body initiated the celebrated 1937 Dewey Commission, that inquired into the charges made against Trotsky in the Moscow show trials and whose verdict pronounced them a complete frame-up.
Novack produced a number of books on various aspects of Marxism: An Introduction to the Logic of Marxism, America's Revolutionary Heritage, Democracy and Revolution, Empiricism and Its Evolution, Humanism and Socialism, The Origins of Materialism, Polemics in Marxist Philosophy, Revolutionary Dynamics of Women's Liberation, and Understanding History, Marxist Essays.