Sowa spent most of his professional career at IBM, which started in 1962 at IBM's applied mathematics group. Over the decades he has researched and developed emerging fields of computer science from compiler, programming languages, and system architecture to artificial intelligence and knowledge representation. In the 1990s Sowa was associated with IBM Educational Center in New York. Over the years he taught courses at the IBM Systems Research Institute, Binghamton University, Stanford University, Linguistic Society of America and Université du Québec à Montréal. He is a fellow of the Association for the Advancement of Artificial Intelligence.