Tommy is a Scottish former professional rugby union player. He made 55 international appearances for the Scotland national rugby union team 2013–2019, scoring 20 tries which placed him fourth-top try scorer for the country. He played in two world cups and the 2017 British & Irish Lions tour to New Zealand. His regular playing position is wing.

In April 2017 Seymour was named as one of two Scottish players selected for the initial British & Irish Lions squad to tour New Zealand in June and July.[9] While not featuring in any of the test matches he appeared in four games on tour scoring one try against the Highlanders and two tries against the Hurricanes. His three tries meant he was the leading try scorer on tour.