He then married Lucinda "Lucy" Burnham Lees on March 9, 1849; together they had eleven children, six boys and five girls.

He won a seat in the Kentucky Senate in 1857 and resigned in 1859 to run for the United States Congress, but was defeated by Green Adams.

He was elected again to the Kentucky Senate on August 4, 1861, but declined to serve as he had received his commission as colonel July 27, 1861.

By 1860, his total worth was $20,000 (over $694,000 in 2007 dollars), and he owned nine slaves thus making him the sixth wealthiest citizen of Clay County.

Garrard remained with the 7th Kentucky until winter 1862 when he was assigned to the staff of Brigadier General Samuel P. Carter.

While at Milliken's Bend, Louisiana, near the end of March 1863, Garrard lost central vision in his left eye.

On January 17, 1864, he was placed in command of the District of the Clinch, a mixed brigade of infantry and cavalry, posted at Cumberland Gap.

The Brigadier General Theophilus T. Garrard Camp #4, Sons of Union Veterans of the Civil War is named in his honor.