In early 1862 the Fifteenth Texas organized under Col. Joseph Warren Speight. Companies came from Waco and Central Texas as well as Corsicana and Velasco. In the summer the regiment drilled in East Texas before marching to Arkansas in the fall. After a brief time with Randle's Brigade, the Fifteenth Texas in December joined Gen. Thomas Hindman's army in western Arkansas.
In January 1863 Speight received command of a brigade that also included four dismounted Texas cavalry regiments. With Lt. Col. James E. Harrison commanding the Fifteenth Texas, the brigade then marched from Fort Smith through snow to the Red River in February. In April orders sent the regiment and the brigade to Gen. Richard Taylor in Louisiana. The Fifteenth Texas and one other regiment moved to the Mississippi River where they harassed Union outposts and shipping in the summer. Despite problems with illness, the Fifteenth Texas under Maj. John W. Daniel led a successful attack on a Federal force at Stirling's Plantation on September 29. In October the Fifteenth Texas under Harrison became part of Polignac's Brigade. On November 3 Gen. Thomas Green led cavalry and infantry, including the Fifteenth Texas, in a surprise attack that drove back Union troops on Bayou Bourbeau.
In February and March 1864 the regiment and the brigade skirmished with Federal forces at Vidalia and Harrisonburg before rejoining General Taylor for the Red River campaign. At Sabine Crossroads and at Pleasant Hill the brigade joined in an attack on the Union Army that halted its advance on April 8 and 9. The Fifteenth Texas and the brigade harassed the Federal withdrawal down the Red River, but a final engagement at Yellow Bayou on May 18 proved unsuccessful. After a summer attempt to cross the Mississippi River failed, the brigade moved to Arkansas in the fall. In November the Fifteenth Texas returned to Louisiana where it remained through February 1865. Then in March the regiment moved into its home state where it disbanded in May.