He also made significant donations to Harvard College and Princeton University.

While studying theology and medicine under his father, he headed schools in Andover and neighboring towns.

From 1767 to 1775, he served on the council of Sir John Wentworth, 1st Baronet, the governor of the Province of New Hampshire.

[3] In 1762, he became the first major donor of Dartmouth College, when he sent a gift to Eleazar Wheelock.

In 1770, as the college, then named Moor's Charity School, wished to relocate to Hanover, New Hampshire, Phillips donated large sums of money and land to the college.

On August 4, 1743, he married Sarah (Emery) Gilman, a wealthy widow.