Col. Oran Milo Roberts mustered the Eleventh Texas Infantry into service near Houston in the winter of 1861–62. Roberts served as commissioner of the Texas Secession Convention in 1861, chief justice of the Texas Supreme Court, law professor at the University of Texas, and governor of the state from 1878 until 1883. The regiment was composed of ten companies that recruited men from several counties including Nacogdoches, Rusk, Cherokee, Greg, Franklin, Harrison, Titus, Panola, Shelby, San Augustine, Kaufman, Van Zandt, and Hopkins. The staff officers included Nathaniel J. Caraway as major, Thomas H. Rountree as major, Andrew J. Coupland as lieutenant colonel, James H. Jones as lieutenant colonel, William G. Engledow as lieutenant colonel, W. M. Ross as quartermaster, John H. Douglas as commissary, and W. H. Christian as adjutant. The regiment served in the Trans-Mississippi Department throughout the war. They first served with the Army of New Mexico before operating in Texas, Louisiana, and Arkansas.
The regiment was attached to the Army of New Mexico on March 1, 1862, but there are no records that it participated in any engagements that far west. In May of 1862 Colonel Roberts had a total of 1,338 men at Camp Lubbock in Harris County of which only 408 were fit for duty. They remained stationed in East Texas from May through August of 1862. Soldiers from the Eleventh Texas Infantry were furnished with cloth for tents, knapsacks, and for some clothing, by the Texas State Penitentiary at Huntsville, Texas. The regiment left Camp Lubbock on May 30, 1862, and arrived at Camp Clough near Tyler, Texas, on June 20, 1862. The unit was then assigned to Gen. Benjamin McCulloch's Division within Gen. Horace Randal's Brigade. On September 30, 1862, they were reassigned to the First Division of the Second Brigade in the Trans-Mississippi Department under the command of Gen. Edmund Kirby Smith. They were involved in operations within the LaFourche District of Louisiana from October 24 to November 6, 1862. The regiment spent the winter of 1862–63 near Little Rock in Central Arkansas. On January 14, 1863, the regiment was reassigned to Gen. John Walker's Division and was involved in an engagement at Bayou Teche. From March 31 to April 17, 1863, the regiment was involved in operations from Milliken's Bend to Carthage, Louisiana. On April 1, 1863, the Eleventh Texas Infantry was assigned to the District of Western Louisiana in the Trans-Mississippi Department with General Walker's Texas Division.
From April 9 to May 14, 1863, the unit was involved in operations in the Teche country of Western Louisiana. They participated in engagements at Fort Bisland at Bethel Place from April 12–13, 1863, and at Irish Bend on April 14. The regiment also saw action on April 17, at Bayou Vermillion. On May 22, 1863, the regiment was involved in a skirmish at Barre's Landing, and on June 7, they saw action at Millikens's Bend and Young's Point. During the summer of 1863 the regiment saw action at LaFourche Crossing, Brasher City, Cox's Plantation, and Donaldsonville. The Eleventh Texas Infantry was involved in constant action during the fall of 1863, and from September to October they were engaged at Morgan's Ferry, Sterling's Plantation, Bayou Vermillion, Opelousas, Barre Landing, and Washington. In November they participated in fighting at Grand Coteau, Bayou Bourbeau, Carrion Crow Bayou, Buzzard's Prairie, Bayou Vermillion, and Camp Pratt. At the battle of Bayou Bourbeau on November 3, 1863, the Eleventh Texas with 355 men suffered 4 killed, 15 wounded, and 32 missing.
On December 31, 1863, the Eleventh Texas Infantry was assigned to Sabine Pass in the District of Texas within the Trans-Mississippi Department. In the spring of 1864 they were again ordered to Louisiana where they participated in the Red River campaign at Fort DeRussy, Franklin, and Natchitoches during March. The unit assisted in capturing over 2,000 prisoners, 20 pieces of artillery, and 200 wagons of arms. The next month they were engaged in numerous engagements including Wilson's Farm, Carroll's Mill, Mansfield, and Pleasant Hill in Louisiana. The battles of Mansfield and Pleasant Hill on April 8 and 9, 1864, were the most important of all the engagements. This bloody two-day encounter was the key to halting Gen. Nathaniel Banks's Red River campaign and prevented the capture of Shreveport and the invasion of Texas. At Mansfield the Eleventh Texas suffered two killed, six wounded, and two missing. At the battle of Pleasant Hill the regiment sustained three killed, eighteen wounded, and none missing.
The Eleventh Texas Infantry was then assigned to Arkansas from April 16 to May 3, where they saw action at Poison Springs, Mark's Mills, and Jenkins' Ferry. The battle of Jenkins' Ferry was described as "a nightmare to both armies" made worse by eighteen hours of continuous rain. The Texans were forced back with heavy losses, including three brigade commanders. The Eleventh Texas Infantry had nine killed and thirty-nine wounded during the battle. During the summer of 1864 the Eleventh Texas Infantry was ordered to Shreveport, Louisiana, then to Marshall, Texas, and then again to Hempstead, Texas. In September of 1864 the unit was reassigned to Gen. John H. Forney's First Texas Division within Gen. Robert P. Maclay's Third Texas Brigade. On September 30, 1864, the regiment was attached to the Third Texas Brigade with the First Texas Division in the Trans-Mississippi Department. Colonel Roberts retired from command of the Eleventh Texas Infantry on October 19, 1864, due to poor health. Col. James H. Jones took command of the regiment on December 31, 1864, for the remainder of the war.
The Eleventh Texas Infantry was assigned to guard prisoners near Tyler, Texas, in early 1865. The regiment returned to Hempstead, Texas, on April 16, 1865, and was included among the Confederate forces in the Trans-Mississippi Department that surrendered at Galveston on June 2, 1865. Records indicate however that the unit was disbanded at Hempstead on May 26, 1865.