Georges Theunis started his career in the Empain group, where he was an administrator and later the president of the board of ACEC.

After the war he was involved in the Paris Peace Conference, in 1919 and served as the Belgian delegate to the Reparations Commission.

In 1926 Theunis joined the newly formed council of Regency of the National Bank, together with Emile Francqui, and remained a member until the war, except for two breaks during his ministerial duties.

As regents of the NBB, both Theunis and Francqui represented the power which the large private banks had gained since 1926.

During World War II he served as a special ambassador to the United States of America.