His parents were John Charles Phillips Jr. (1838–1885), who married Anna Tucker in London, England on October 23, 1874.

His older brother was John Charles Phillips (1876–1938), a prominent zoologist, ornithologist and environmentalist.

[1] His first political job was working as a private secretary in London to Joseph Hodges Choate, the United States Ambassador to the Court of St. James.

[1] In 1936, he was appointed as the Ambassador to Italy, which was then led by Benito Mussolini, in the immediate aftermath of that country's invasion of Ethiopia.

[1] In October 1942, Phillips was appointed as a personal representative of President Franklin D. Roosevelt and served in India.

In 1943, he was made a Special Advisor on European political matters to General Dwight D. Eisenhower, with the rank of ambassador.

[1] Phillips retired officially in 1944 but returned briefly to diplomatic life in 1945, when he was made a special assistant to Secretary of State Edward R. Stettinius Jr.