Mercy Otis was the sister of the political activist James Otis (Otis, James), who was early involved in events leading to the American Revolution. She received no formal schooling but managed to absorb something of an education from her brothers' tutors. In 1754 she married James Warren, a Massachusetts political leader. Knowing most of the leaders of the Revolution personally, Warren was continually at or near the centre of events from 1765 to 1789. She combined her vantage point with a talent for writing to become both a poet and a historian of the Revolutionary era. She wrote several plays, including the satiric Adulateur (1772). Directed against Governor Thomas Hutchinson (Hutchinson, Thomas) of Massachusetts, the play foretold the War of Revolution.

The Defeat, also featuring the character based on Hutchinson, followed, and in 1775 Warren published The Group, a satire conjecturing what would happen if the British king abrogated the Massachusetts charter of rights. The anonymously published The Blockheads (1776) and The Motley Assembly (1779) are also attributed to her. In 1788 she published Observations on the New Constitution, whose ratification she opposed.

Warren corresponded with her friend Abigail Adams (Adams, Abigail) on her belief that the relegation of women to minor concerns reflected not their inferior intellect but the inferior opportunities offered them to develop their capacities. In 1790 she published Poems, Dramatic and Miscellaneous, a collection of her works. In 1805 she completed a three-volume history titled A History of the Rise, Progress, and Termination of the American Revolution, which remains especially useful for its knowledgeable comments on the important personages of the day. The book's sharp comments on John Adams (Adams, John) led to a heated correspondence and a breach in her friendship with the Adamses that lasted until 1812.