He was born in Boston, Massachusetts, in 1766, the son of John Coffin, and left there with his family in 1775 at the start of the American Revolution.
In 1796, he was elected to the Legislative Assembly of Lower Canada for Bedford County.
Coffin was named a justice of the peace for Montreal district later that year.
He was replaced by James FitzGibbon as adjutant general at the start of the Upper Canada Rebellion.
Coffin was friends with the Edinburgh-born New England bookseller and publisher John Mein.