James Robertson Dawson Jr. received his B.A. degree in 1928 and his Doctor of Medicine degree in 1931, both from Vanderbilt. He then became an instructor in the Department of Pathology at Vanderbilt, where he remained until 1934. During this early portion of his career, Dawson devoted much of his research effort to virology and particularly to viruses affecting the central nervous system.

In 1934 Dawson left Vanderbilt to become an Assistant in Pathology and Bacteriology at the Rockefeller Institute for Medical Research, where he worked intensively with the rabies virus. He then became an Instructor in Bacteriology and Immunology at Cornell, where he stayed until 1938, at which time he returned to Vanderbilt as Associate Professor of Pathology. Dawson was eventually promoted to Professor and worked in this capacity until 1949. He served as Professor and Head of Pathology at the University of Minnesota from 1949 to 1970. He was Professor of Pathology at the University of Mississippi Medical Center from 1970 until his retirement in 1976.