After a few years' absence from physics she was invited to join McGill as a Demonstrator in 1940, and was subsequently appointed as an Instructor in the wartime program on the training of Radio Mechanics. This was followed by an appointment as a Sessional Lecturer in 1943, then as a full-time Lecturer also in 1943, an Assistant Professor in 1947 and an Associate Professor in 1954. After her retirement in 1970, the University invited her to become an Honorary Visiting Professor, a post that she held until her death in 1979.
During her long career at McGill she taught and helped a very large number of students. Optics was her specialty and her "Advanced Light" laboratory represented one of the finest opportunities for training in classical optics available anywhere at the time. In all areas of classical physics her background and her ability to teach made an impact on McGill's undergraduate physics program in the years following the Second World War.
Her contributions to McGill were not only in teaching, research and counseling. Upon her death in November 1979, she gave a large sum of money to the University to be used for medical research and for the Department of Physics. The Department uses the revenue from this money for the support of research and also has established the Anna I. McPherson Lectures in Physics in her honor. The mandate of these lectures is to bring distinguished physicists to the Department for a few days to give two lectures as well as to meet with the staff and with the students. In establishing this lectureship and by naming the small astronomical observatory of the Department of Physics in her memory, the members of the Department of Physics seek to acknowledge her outstanding generosity and her many valued academic contributions.