In 1864, Reno took part in the battles of Haw's Shop, Cold Harbor, Trevilian Station, Darbytown Road, Winchester (3rd), Kearneysville, Smithfield Crossing and the Cedar Creek. For his service at Cedar Creek, he was brevetted lieutenant colonel. In January 1865, he entered volunteer service as colonel of the 12th Pennsylvania Volunteer Cavalry, later commanding a brigade against John Mosby's guerrillas. Reno received an appointment as brevet colonel in the Regular Army (United States), to rank from March 13, 1865, for "meritorious services during the war." On January 13, 1866, President Andrew Johnson nominated Reno for appointment to the grade of brevet brigadier general, U.S. Volunteers, to rank from March 13, 1865, and the United States Senate confirmed the appointment on March 12, 1866.