McClellan used almost 41,000 men against nearly 32,000 Confederates.
The Confederates lost about 1,500 men, while the Union suffered nearly 2,300 casualties.
McClellan was determined to pursue the Confederates withdrawing from the Yorktown defenses. He sent all his cavalry, under Stoneman and supported by Hooker's infantry division, chasing after. The cavalry met JEB Stuart's riders about eight miles from Williamsburg and quickly pushed them back on their support, Longstreet's division. Magruder had built a secondary line across the Peninsula just east of Williamsburg, where two creeks narrowed the distance to defend.
Longstreet knew he had to buy time for the supply train and artillery to move up the muddy roads, and fought hard. He repulsed Hooker's attack on Fort Magruder, an earthwork in the center of the line, then counterattacked. At first he threatened to overwhelm the Union left flank, but Phil Kearny's division arrived to stabilize the position. Hancock's brigade then moved to threaten the Confederate left flank, occupying two abandoned redoubts. Longstreet's counterattack was unsuccessful (Jubal Early's brigade suffering heavily), but Hancock's local success was not exploited. The Confederate army continued its withdrawal during the night.