Trammell's big break came when he landed the role of Sam Merlotte on the HBO series True Blood. In 2013, Trammell played Darrell Mackey in the drama film White Rabbit. Trammell played Hazel's (Shailene Woodley) father, Michael Lancaster, in the 2014 film The Fault in Our Stars, based on the novel of the same name by John Green.