When Thomas was eight, his father died, leaving a lot of responsibility to help his mother and sister. In 1848, Missionaries from the Church of Jesus Christ of Latter-day Saints visited the Hillyard family. Thomas' mother joined the Church earliest sometime between 1849 and 1850, and Thomas joined in 1850.
Thomas married Mary Ann Heaps on July 28, 1850 in Doddington, England. The Hillyard family began preparations to move to Utah and sailed on the Marshfield. They sailed from Liverpool on April 8, 1854 and arrived in New Orleans, Louisiana on May 29. The pioneer company that the Hillyard family joined is unknown, but the family did arrive in the Salt Lake Valley the same year.
In Salt Lake, Thomas began using his carpentry skills to good use. In 1857 during the Utah War, Thomas was called to bear arms and he moved in family to Provo, Utah to be safer. While in Provo, Thomas was hired by LDS Apostle John Taylor to outfit his wagons and teams for the trip from and from Provo. After the conflict, the Hillyard family moved back to Salt Lake City in April of 1859.
In 1860, the Hillyard family moved to Richmond.