His sister, Elizabeth Barclay Moffat (1898–1993), was married to John Campbell White (1884–1967), the United States Ambassador to Haiti and Peru.

Moffat continued his diplomatic career in the post of secretary to the American legation in Bern, Switzerland, from 1927 to 1931, and as the U.S. Consul General to Australia from 1935 to 1937.

[10] In his obituary, The New York Times remarked that "even in war, when death is knocking at such a multitude of doors, the loss of a trusted public man in the flower of his age and his powers is lamentable".

[1][19] A service was held for Moffat at Christ Church Cathedral in Ottawa, which was attended by Prime Minister Mackenzie King and Sir Suldham Redfern, who represented the Earl of Athlone, Governor General of Canada.

[20] Moffat was a lineal descendant of John Jay, negotiator of the Treaty of Paris, Secretary of Foreign Affairs and first U.S. Chief Justice.