- Went to high school with Jennifer Garner, and the two later appeared in the 1996 made-for-TV movie Harvest of Fire.
- Studied philosophy and linguistics in college, but got hooked on acting during his last semester at Brown after a friend suggested he audition for a play, even though he had no previous experience.
- Moved to New York City after college in 1993, and his persistence paid off with a major part in a 1998 revival of Eugene O'Neill's Ah, Wilderness! The role earned him a Tony Award nomination for Best Featured Actor in a Play, an Outer Critics Circle Award nomination for Best Actor in a Play, a Theatre World Award and a Clarence Derwent Award for Most Promising Male.
- A scene from the first season of True Blood where his character runs naked through the woods was shot at Lake Bistineau in Louisiana, on land that used to be owned by a distant relative of Trammell's.
- His mother Betsy Trammell (née Foote) is a distant relative of deceased historian Shelby Foote.
- Became a father when girlfriend Missy Yager gave birth to twin boys on August 9, 2011.