It was assumed he would follow a career in business but Hallowell developed interests in sociology and became first a social worker for the Family Society.
Hallowell played a central role in developing Northwestern's Anthropology department as a major centre in the United States for the study of the discipline.
[2] Hallowell's main field of study was Native Americans including the Abenaki, the Montagnais-Naskapi but particularly the Ojibwe, about whom he wrote nearly forty individual papers, articles, chapters, and one monograph.
[2] In his research he utilised anthropological techniques such as ethnography and linguistic studies but also methods drawn from clinical psychology - mainly the Rorschach, or ink-blot, test - to assess the personality structures of Native American populations.
[2] His students included the anthropologists Melford Spiro, Anthony F. C. Wallace, Raymond D. Fogelson, George W. Stocking, Jr., Regna Darnell, Erika Eichhorn Bourguignon, James W. VanStone and Marie-Françoise Guédon.