In a career spanning 37 years, Mr. M. D. D. Pieris, as a member of the then Ceylon Civil Service and thereafter, The Sri Lanka Administrative Service, held numerous senior positions in Government, including those of Secretary to the Prime Minister, Secretary to the Ministry of Agriculture, Food and Co-operatives; Public Administration, Provincial Councils and Home Affairs; and Education and Higher Education.

He had also at various times, in addition to his duties, been a Chairman, a Director or member of the Council of over 25 Corporations, other Statutory Institutions, Universities and Post Graduate Institutes.

He has been Chairman of two Presidential Committees and a member of two Presidential Commissions, one relating to Finance and Banking and the other relating to Public Sector salaries.

Since his retirement from the Public Service, he holds various positions in the private sector including that of Deputy Chairman, Mercantile Merchant Bank Limited. He also still assists many public institutions in various capacities.

He is currently Chairman Pro-tem of the Bandaranaike Centre for International Studies and is a member of the Board of the Regional Centre for Strategic Studies.

Mr. Pieris has also been awarded two of the highest National Honours, that of Desabandu and Deshamanya.