In 1927, he succeeded Ven. Suriyagoda as lecturer in the then
University College, Colombo to lecture in English on
Sinhala,
Pali and
Sanskrit for the University of London degree examinations. When the
University of Ceylon was founded in 1942, he became the Professor of Pali and Buddhist Studies. Serving as the Head of the Department of Pali, he went on to serve as the Dean of the Faculty of Oriental Studies, University of Ceylon. His research on Buddhism and
Buddhist Civilization was extensive and he was the Editor-in-Chief of the Encyclopaedia of Buddhism. He contributed research papers and publications to the
Pali Text Society of London under the patronage of scholars like
Rhys David and Miss I. B. Horner. From 1927, he was twice elected the Joint Secretary of the
All Ceylon Buddhist Congress. Thrice he was the Vice-President and functioned as its President from 1939 to 1957. On his departure from the University of Ceylon, he was appointed
Professor Emeritus. During his tenure in office, he saw to it that the All-Ceylon Buddhist Congress constructed a new building for its headquarters in Buller's Road (now
Bauddhaloka Mawatha). He took a delight in the activities of the Viharamahadevi Girls' Home,
Biyagama and was responsible for the establishment of boys' homes at Panadura and
Ja-Ela. During his presidency of the Buddhist Congress for 25 years, he addressed 20 of its annual sessions. His most significant publication is the
Malalasekara Sinhala-English Dictionary. It was first published in 1948 and is currently up to its fifth edition, which was released in 2014. Of equal importance is the
Dictionary of Pali Proper names. He was an ardent member of the
Royal Asiatic Society of Ceylon. He represented Ceylon at several parleys abroad, notably: Conference on Living Religions (London, 1924), Conference on World Religious (London, 1936), Association of Occidental (Western) and Oriental Philosophers (Hawaii, 1949), Association of Indian Philosophers – India, meeting of the Pakistani Philosophers (Karachi, 1953), and the Seminar on Religions for Peace, (San Francisco, USA, 1965). He presented numerous essays, write-ups and literary contributions, and delivered radio talks on Buddhist and religious/cultural matters and Social service assignments. He was the founder president of the World Fellowship of Buddhists inaugurated within the
Temple of the Tooth, Kandy in 1950 at the suggestion of the All Ceylon Buddhist Congress. He was president of the
World Fellowship of Buddhists from 1950 to 1958 as well as the Ceylon Arts Society; ==Diplomatic career==