Coulson was born in Manchester, and attended Westminster School in London on an academic scholarship. He was a member of the UK's National Youth Music Theatre from 1990–1997, and went on to the University of Cambridge, where he received a degree in English from Clare College in 2000. While at university, he played the M.C. (Master of Ceremonies) in Cabaret, Arturo Ui in The Resistible Rise of Arturo Ui and Claire in The Maids, as well as appearing in film and television.
He also wrote the lyrics and book for a rock musical called The Fallen which was performed at Bedford Modern School in 1998.
Coulson gained worldwide attention and popularity for his role in 2002's Harry Potter and the Chamber of Secrets, in which he portrayed a 16-year-old Tom Riddle, even though Coulson was 24 years old at the time. However, in 2007, Director David Yates indicated on MTV that Coulson would not reprise his role in Half-Blood Prince, since, at 29, he was now too old.
As of 2010, Coulson currently resides and works in New York City as an actor and Director.
