Fort Sullivan is defended on the morning of June 28 by Colonel Moultrie, commanding the 2nd South Carolina Regiment and a company of the 4th South Carolina Artillery, numbering four hundred and thirty-five men.

At around 9:00 am this morning, a British ship fires a signal gun indicating all is ready for the attack.

Less than an hour later, nine warships sail into positions facing the fort.

Thunder and Friendship anchor about one and a half miles (two point four kilometers) from the fort while Parker takes Active, Bristol, Experiment and Solebay to a closer position about four hundred yards (three hundred and seventy meters) from Sullivan's Island, where they anchor facing broadside to the fort.

Each of these ships begins to fire upon the fort when it reaches its position, and the defenders return the fire.

Although many of Thunder's shots land in or near the fort, they have little effect.

Thunder's role in the action is also relatively short-lived; she has anchored too far away from the fort, and the overloading of her mortars with extra powder to increase their range eventually leads to them breaking out of their mounts.

Owing to shortage of gunpowder, Moultrie's men are deliberate in the pace of their gunfire, and only a few officers actually aim the cannons.

They also fire  in small volleys, four cannon at a time.

General Clinton begins movements to cross over to the northern end of Sullivan's Island.

Assisted by two sloops of war, the flotilla of longboats carrying his troops coms under fire from Colonel William Thomson's defenses.

Facing a withering barrage of grape shot and rifle fire, Clinton abandons the attempt.

Around noon the frigates Sphinx, Syren, and Actaeon are sent on a roundabout route, avoiding some shoals, to take a position from which they can enfilade the fort's main firing platform and also cover one of the main escape routes from the fort.

However, all three ships ground on an uncharted sandbar, and the riggings of Actaeon and Sphinx become entangled in the process.

The British managed to refloat Sphinx and Syren, but Acteon remains grounded, having moved too far onto the submerged sandbar.

Consequently, none of these ships reach its intended position, a piece of good fortune not lost on Colonel Moultrie.

At the fort, Moultrie orders his men to concentrate their fire on the two large man-of-war ships, Bristol and Experiment, which take hit after hit from the fort's guns.

Chain shot fired at Bristol eventually destroys much of her rigging and severely damages both the main- and mizzenmasts.

One round hits her quarterdeck, slightly wounding Parker in the knee and thigh.

The shot also tears off part of his britches, leaving his backside exposed.

By mid-afternoon, the defenders are running out of gunpowder, and their fire is briefly suspended.

However, Lee sends more ammunition and gunpowder over from the mainland, and the defenders resume firing at the British ships; Lee even briefly visits the fort late in the day.

Admiral Parker eventually seeks to destroy the fort's walls with persistent broadside cannonades.

This strategy fails due to the spongy nature of the palmetto wood used in its constructions; the structure quivers, and it absorbesthe cannonballs rather than splintering.

The exchange continues until around 9:00 pm, when darkness forces a cessation of hostilities, and the fleet finally withdraws out of range.

At one point during the battle, the flag Moultrie had designed and raised over the fort is shot down.

Sergeant William Jasper reportedly runs to the battlement and raises the flag again, holding it up and rallying the troops until a flag stand can be provided.

He is credited by Moultrie with reviving the troops' spirits, and later given commendations for bravery.

Counting casualties, Parker reports forty sailors killed and seventy-one wounded aboard Bristol, which has been hit more than seventy times with much damage to the hull, yards, and rigging.

Experiment is also badly damaged with twenty-three sailors killed and fifty-six wounded.

Active and Solebay reported fifteen casualties each.

The Americans report their casualties at only twelve killed and twenty-five wounded.