After earning his doctorate, Goddard taught at Harvard as a junior professor.
In 1975, he moved to the Smithsonian Institution. His own field research has concentrated on the Delaware languages and Meskwaki (Fox). He is also known for work on the AlgonquianMassachusett language, and the history of the Cheyenne language. He has also published on the history of the Arapahoan branch of Algonquian, whose two living representatives are Arapaho and Gros Ventre.
Goddard is a prominent figure in the study of the methodology of historical linguistics. He has played a significant role in critiquing crank historical linguistic work.