In the winter of 1861–62, the Thirty-fourth Texas formed under the leadership of Col. Almerine M. Alexander. The men were recruited in a North Texas area bounded by Red River, Erath, and Palo Pinto counties. Their attitudes ranged from prewar Unionists to secessionists. The regiment moved into the Indian Territory in May 1862 and in the summer joined a cavalry brigade under Col. D. H. Cooper that included the Twenty-second Texas and the Thirty-first Texas. On September 30, 1862, the Thirty-fourth fought successfully at Newtonia, Missouri. Following a retreat into Arkansas, changes in command and illness disrupted the regiment during the fall. As a result, orders took away the men's horses and left increased morale problems. Despite those problems, the Thirty-fourth Texas Dismounted Cavalry fought at Prairie Grove, Arkansas, on December 7. The brigade then marched to Fort Smith in January 1863 and through snow to the Red River in February.
Orders in April sent the regiment and brigade to Louisiana. Following infantry drills, the Thirty-fourth and two other regiments formed a brigade under Gen. Camille de Polignac in July. During the fall Lt. Col. John H. Caudle became commander of the regiment, which served in the area from Alexandria to the Mississippi River until the end of the year.
After skirmishes at Vidalia and Harrisonburg in February and March 1864, the Thirty-fourth Texas and the brigade joined Gen. Richard Taylor to oppose the Union Red River campaign. At Sabine Crossroads and at Pleasant Hill on April 8 and 9, the regiment helped drive back the Union advance. The brigade then harassed the Federal army and navy as they withdrew down the Red River. A final attack at Yellow Bayou on May 18 did not break through. An attempt to send the brigade across the Mississippi River failed in August. The Thirty-fourth Texas then marched to Arkansas in the fall and returned to Louisiana during the winter. In March 1865, the regiment received orders to join a new brigade, which moved to Texas and disbanded in May.