Native to Glasgow, Scotland, Boyd trained at the Scottish Academy of Music and Drama before setting off to become an actor. Besides acting, he also came away a skilled musician playing bass, drums and guitar, as well as singing.
He crafted his skill on stage landing roles in productions like "The Chick Nerds", "Britannia Rules" and "Trainspotting". Going on to television, Boyd started working on the Scottish series Target followed by appearances in "Coming Soon" (1999) and "Judie and the Cadillacs" (1999). He landed his first role in feature work playing the loan shark in "Urban Ghost Story" (1998), alongside Jason Connery (Smallville) and James Cosmo (Game of Thrones). Following this, he was cast in The Lord of the Rings trilogy, one of the most successful and critically acclaimed series of films to make it to the silver screen. He played Peregrin “Pippin” Took, a Hobbit of the Shire, and one of Frodo Baggins's (Elijah Wood) youngest but closest friends. He was one of the four Hobbits to take part of the Fellowship of the Ring, which also included Frodo, Merry (Dominic Monaghan), and Samwise (Sean Astin).
Since then, he has appeared in several films including "Master and Commander: The Far Side of the World" (2003) starring Russell Crowe, "The Flying Scotsman" (2007) alongside Johnny Lee Miller, and in Irvine Welsh's "Ecstasy" (2012) with Kristin Kreuk (Smallville). Of late, he played Nick Chopper (aka The Tin Man) in the "Dorothy and the Witches of Oz" (2012), which also starred Christopher Lloyd, Sean Astin, Mia Sara, Lance Henriksen, and Jeffrey Combs, as well as starring in the scifi-comedy "Space Milkshake" (2012) with Amanda Tapping, George Takei, Robin Dunne, and Kristin Kreuk.