Born in Dysart, Fife, he enlisted in the Marine Forces at the age of 23 and was stationed in North America during the French and Indian War, serving at the rank of captain.

Arriving in Boston in 1774 at the rank of major, he fought in the 1775 battles of Lexington and Concord during the outbreak of the American War of Independence.

John Pitcairn entered the Marines when he was twenty-three,[2] was commissioned as a lieutenant in 1746, served in Canada during the French and Indian War as a captain, and was promoted to major in 1771.

In 1774 he arrived in Boston, Massachusetts, in command of 600 Marines assigned to support the royal governor, General Thomas Gage, in the increasingly resistive colony.

[4] John Trumbull's painting of the Battle of Bunker Hill depicts Pitcairn's death, though with several errors and anachronisms.

Pitcairn is shown falling at the crest during its capture from the American force, while he was actually shot starting to climb the hill.

Later, in 1770, Robert Pitcairn was aboard an East India Company ship that vanished without trace en route to the Comoro Islands.