Vesnić was the diplomatic representative from Serbia at the Paris Peace Conference at Versailles in June 1919. He was married to the American Blanche Ulman who was acquainted with President Wilson's wife. Vesnić travelled to Washington prior to the Peace Conference to meet with Wilson and explain the Serbian position with respect to the break-up of the Austro-Hungarian Empire. He also represented Serbia at the League of Nations Conference in January 1919.