He was placed first in the First Class at the Advocates Intermediate Examination the same year. The following year, he was placed first in the First Class at the Advocates Final Examination of the Ceylon Law College and was admitted to the Ceylon Bar in 1955.
In 1958 Mr. Kadirgamar was admitted to the United Kingdom Bar as a Barrister at Law, Inner Temple. On completion of his studies at Balliol College, Oxford, he was awarded a B.Lit. by the University of Oxford in 1960. He was the President of the Oxford Union in 1959.
Mr. Kadirgamar practiced law at the Ceylon Bar from 1960 to 1971 and before the Privy Council, London, in the years 1955 to 1960 and 1971 to 1974, practicing among the eminent barristers of the time.
He functioned as a Consultant to the International Labour organization (ILO) in Geneva in 1974. In 1976 he joined the World Intellectual property Organization (WIPO) and served as a Director until 1988 advising all governments of Developing Countries in Asia and the Pacific on Intellectual property.
On resumption of practice at the Sri Lanka Bar, he specialized in Commercial, Administrative, Intellectual Property, Industrial and Labour, Constitutional and International Law. He was appointed President's Counsel in 1991.
Mr. Kadirgamar served as a member of the Advisory Committee on Intellectual Property for the Government of Sri Lanka and the Foreign Affairs Study Group appointed by the President of Sri Lanka. He chaired the Committee for Up-grading Consultancy Services in the Construction Industry of Sri Lanka.
He was a member of the Panel of Consultants on Law Reform in Sri Lanka appointed by the Minister of Justice. He was also the one-man Commissioner appointed by Amnesty International to investigate the Catholic-Buddhist crisis in Vietnam in 1963.
He is the author of a number of articles published in international legal journals such as the Modern Law Review, The South African Law Journal, The Conveyancer, property law.
Mr. Kadirgamar has participated with distinction in cricket, athletics and rugby football and continues his interest in sports.