Born in 2978 3A, Thomas played a significant role in the Battle of Bywater and fought alongside his father against Bill Ruffin and the Ruffians. Afterwards, he married Marigold Gamgee, the younger sister of Samwise Gamgee. After his marriage, Thomas began to serve briefly as Deputy-Mayor of Michel Delving until he resigned on the day of Bilbo's 111th birthday.
When Sam and his friends left the Shire, Thomas and his family were concerned of this and grew worried. A month later, Thomas and his wife received word from Will Whitfoot that Sam, Frodo, Merry, and Pippin were in Rivendell and set themselves on a quest to destroy the One Ring with the company called the "Fellowship of the Ring". He eventually joined the Shire Company due to his skills and travelled south to where evil was beginning to rise in the corners of Middle-earth.
Thomas would soon take part in the Battle of Pelennor Fields where he took down a few warg riders that were retreating from the battlefield. He later volunteered in gathering the wounded and bringing them to Minas Tirith to be healed. Thomas and Marigold was very happy to see Merry and Pippin alive, but were concerned that Frodo and Sam were not with them. When Gandalf the White revealed that the two hobbits were in Mordor, Thomas held hope that they were still alive. He soon travelled to the Black Gate with the armies of the Free Alliance and prepare for their final encounter with Sauron. He was shocked to learn when the Mouth of Sauron revealed Frodo's Mithril vest, believing that both Frodo and Sam were dead, but it turns out to be false. Thomas fought valiantly in the Battle of Morannon and died in the fight. Rosie, Pippin, and Merry gravely mourned his lost and buried him in the fields of Pelennor with the other deceased fighters.