Not much is known of the character's early life as it was never revealed however, we do know he is from Ireland as he is Irish.
Although Tommy isn't much seen on board, it is shown how he met Jack Dawson and Fabrizio De Rossi on Titanic's deck, and also being quite fascinated by Jack's drawings. Unlike his friends, Thomas did not fall in love aboard the ship and if he did, which is highly unlikely, it is never seen. Tommy is also seen at the Third Class Party, smoking and having a good time. He even arm wrestled with a fellow Third Class passenger but lost despite asking for another round. In a deleted scene, Tommy is admiring Jack's artwork, saying "This is very good." Tommy is seen smoking onboard various times.
Tommy was awakened by the ship's collision with the iceberg and his cabin immediately started flooding. He is shown along with Fabrizio and various other third-class passengers fleeing for safety, taking a lifebelt from Steward 2. As the ship continued to sink, Tommy and Fabrizio meet Jack and Rose behind a locked gate blocking the passengers behind it with it guarded by several crew members including one with a pistol. He goes up to the gate and yells at the crew. He tells Jack and Rose that the gate is guarded by the crew. Jack then goes to another exit gate guarded by Steward 2 and rams it down with the help of Tommy and Fabrizio. Tommy tries to find a lifeboat for all four of them to get off safely. Upon failing, Jack then tells Tommy and Fabrizio to go to the other side of the ship to find a lifeboat. They find Collapsible Lifeboat A being run by William Murdoch, who won't let him, Fabrizio, Caledon Hockley and a angry mob of men board. Murdoch then threatens to shoot anybody who tries to go to the lifeboat. A man tries to do so but gets shot to death. However, someone accidentally pushed Tommy fowards, leading Murdoch to think that he tried to go to the lifeboat, and therefore, Murdoch shot Tommy in his left lung before thinking, and afterwards, Murdoch commits suicide when he understands that he killed an innocent man. Tommy collapses while coughing up blood before dying in Fabrizio's arms.
In order to survive the rough waters around the ship, Fabrizio takes Tommy's lifebelt by untying it and strapping it on to him. However, he later dies when a funnel falls on him.
He was played by Irish actor Jason Barry.