He was the son of Wayne MacVeagh, who was Attorney General of the United States in the administration of President James Garfield.

He earned a law degree at Columbia University in 1883; and he was admitted to the New York State Bar.

He was commissioned Ambassador Extraordinary and Plenipotentiary on September 24, 1925, during a recess of the Senate.

In the 1910s he built an extensive summer estate called Fasnacloich (named after a Scottish manor originally in his wife's family) in Harrisville, New Hampshire, not far from his brother Franklin's Knollwood estate.

The estate, now listed on the National Register of Historic Places, is an homage to English and Scottish medieval houses, featuring terraced gardens and imported Italian fountains.