In 1938 he began his international service at the Economic and Financial Organization of the League of Nations, where he served until 1943.

[1]: 7  He was a member of the Netherlands delegations to the 1944 Bretton Woods Conference establishing the International Monetary Fund and to the Atlantic City conference that established the United Nations Relief and Rehabilitation Administration (UNRRA).

Subsequently, in addition to engaging in a full agenda of research and writing, he served as a Consultant with the World Bank, as a Senior Adviser to the Development Center of the Organisation for Economic Co-operation and Development (OECD), and, after 1987, as President of the Per Jacobsson Foundation.

The International Monetary Fund recently honored Polak by naming its annual research conference after him.

In addition, Dr. Polak was a awarded the rank of Commander in the Order of the Orange-Nassau, a rare distinction.