In December 1775, at the age of 21, the volunteer-soldier Banastre Tarleton sailed from Cork to North America, where the American War of Independence (1775–83) had broken out. Tarleton sailed with Lord Cornwallis as part of an expedition to capture the southern city of Charleston, South Carolina.[6] After that expedition failed, at the Battle of Sullivan's Island (28 June 1776), Tarleton went north to join the main British Army under command of General William Howe, in New York.

Under the command of Colonel William Harcourt, Tarleton, as a cornet, was part of a scouting party sent to gather intelligence on the movements of General Charles Lee, in New Jersey. On 13 December 1776, Tarleton surrounded a house in Basking Ridge, and forced Lee, still in dressing gown, to surrender, as he threatened to burn down the house. General Lee was taken to New York as a prisoner of war. He later was used in an exchange of prisoners.

Tarleton was brevetted to lieutenant-colonel in the 79th Foot on 26 June 1781. After other missions, Cornwallis instructed Tarleton to hold Gloucester Point, during the Siege of Yorktown. On 4 October 1781, the French Lauzun's Legion and the British cavalry, commanded by Tarleton, skirmished at Gloucester Point. Tarleton was unhorsed, and Lauzun's Legion drove the British within their lines before being ordered to withdraw by the Marquis de Choisy. The Legion suffered three Hussars killed with two officers and eleven Hussars wounded. Fifty British were killed or wounded, including Tarleton. The British surrendered Gloucester Point to the French and Americans after the surrender at Yorktown in October 1781. He returned to Britain on parole, finished with this war at the age of 27.