On September 11, 1861, Sorrel received his commission as captain and was assigned as General Longstreet's adjutant-general. He was promoted to major on June 24, 1862 and to lieutenant colonel on June 18, 1863. He served under Longstreet until October 1864, when he was appointed brigadier general. Sorrel then commanded Sorrel's Brigade of Maj. Gen. William Mahone's division at Petersburg and Hatcher's Run, and was wounded in both battles.