McCarthy attended the United States Military Academy from 1957 to 1961 and graduated with a Bachelor of Science degree.

[6][5] Upon graduation from West Point, McCarthy was commissioned a Second Lieutenant in the Infantry branch of the United States Army.

[5][1] From 1969 to 1975, McCarthy served on the East Bridgewater Board of Selectmen.

[6][7][10][11] He was also an unsuccessful candidate for the United States House of Representatives seat in Massachusetts's 10th congressional district in 1980.

[12][7] From 2001 to 2015, he served as Register of Probate for Plymouth County, Massachusetts.