When the Civil War broke out, Ector enlisted as a private in the 3rd Texas Cavalry Regiment of the Confederate army. He was soon elected lieutenant. He served as adjutant to Brigadier General Joseph L. Hogg and saw action in Texas and Arkansas. He was promoted to colonel and given command of the 14th Texas Cavalry Regiment. Then in August 1862, he was promoted again to brigadier general and assigned command of a brigade. He fought at the Battle of Murfreesboro in Tennessee and Chickamauga in Georgia. His men and he were then assigned duty in Mississippi, returning in time for the Atlanta Campaign in the summer of 1864.