In 1936, when the Spanish Civil War started, he joined the Fifth Regiment. The following year, as a high-ranking army officer, commanding the 11th division of the republican army, Líster was instrumental in the defense of Madrid and other important military actions. In October 1936 he led a mixed brigade in the ill-fated Republican counteroffensive at Seseña. As a divisional commander, he helped stall the Nationalist attack along the Jarama and played a significant role within the successful Republican counterattack at the Battle of Guadalajara.