In 1975, James Callahan received the Lester R. Ford Award of the Mathematical Association of America and at Smith he has received the Faculty Distinguished Teaching Award and the Sears–Roebuck Foundation Award for Teaching Excellence and Campus Leadership. He has made research trips to England and France.

Callahan was the director of the Five College Calculus Project (funded by the National Science Foundation), and co–author of Calculus in Context (W. H. Freeman & Co, 1995). He wrote The Geometry of Spacetime (Springer–Verlag, 2000) an undergraduate text in mathematics about relativity, as well as Advanced Calculus: A Geometric View (Springer–Verlag, 2010).

Callahan's interests include geometry, dynamical systems, chaos and fractals, catastrophe theory, relativity, most areas of applied analysis and building things.