He was responsible for raising and leading the 1st Canadian Regiment of the Patriots' Continental Army during the invasion of northeastern Canada, and continued to serve in the war until 1781.

As early as August, he had been in contact with General Philip Schuyler, mostly through the efforts of John Brown, an American spy.

On the 28th, they sent word back to Montgomery with news that spurred him to begin the invasion: the British had almost completed ships capable of threatening the American naval superiority on Lake Champlain.

On September 15, he reported to Schuyler that militia under his control had cut off Fort Chambly from communication with Montreal, and that Brown and Ethan Allen were raising additional troops and guarding the southern shore of the Saint Lawrence River.

On November 20, Montgomery made him a colonel in the Continental Army,[11] and gave him command of the 1st Canadian Regiment,[12] consisting mainly of the troops he had recruited.

Livingston was in command of Verplanck's Point on the Hudson River in September 1780, when he played a crucial role in the unmasking of Benedict Arnold's treachery.

While on guard duty, his troops fired on the British sloop of war Vulture, forcing that vessel to retreat southwards.

André was hanged as a spy, and Arnold, knowing that his plot had been discovered, managed to escape to the British lines.