Demobilized as a major in 1945, he was a lecturer in history at the University of Liverpool from 1946 to 1949. In 1950, he was appointed Raffles Professor of History at the new University of Malaya in Singapore. While there, he initiated an important series of historical monographs on the history of Malaya, publishing the first in 1960. A movement developed in the mid-1950s to establish two campuses, one in Kuala Lumpur and one in Singapore. Parkinson attempted to persuade the authorities to avoid dividing the university by maintaining it in Johor Bahru to serve both Singapore and Malaya. His efforts were unsuccessful and the two campuses were established in 1959. The Singapore campus later became the University of Singapore.