After leaving Shortland Street, Henderson jumped the pond to appear on Australia's Home and Away in 1996 as well as a few other TV shows. It was a stepping stone on his way to Hollywood, where in 2002 he landed a predominant role in the creepy thriller, The Ring.
Starring alongside Naomi Watts, Henderson's character, Noah, tries to help uncover the mystery of a sadistic VHS tape.
2. Toxic
Pre-meltdown, Britney Spears was killing it and her song Toxic is still one of her biggest tracks. Our very own Henderson stars as Britney's love interest/target in the music video.
The clip shows Spears kissing and poisoning Henderson in a hotel room. The Toxic music video led Henderson to his first leading movie role in the film Torque, made by the music video's director Joseph Kahn. The movie wasn't great, but Henderson soon moved on to other films, like 2004's romantic comedy Bride and Prejudice, where he starred as Mr Darcy.
In 2006 Martin Henderson joined massive ensemble film Smokin' Aces - a post-Ocean's 11 assassin flick.
Henderson joined the ranks of Ryan Reynolds, Ben Affleck, Jeremy Piven, Ray Liotta, Common and Alicia Keys for the action movie. Again, the film didn't fare well with critics, but it was another chance for Henderson to make a name for himself amongst the stars. He also found roles in Flyboys (2006), Battle in Seattle (2007) and Home by Christmas (2010).
4. Off The Map
After finding other bit parts in movies and TV shows such as the popular House M.D. - where he played a dying patient in 2009 - Henderson eventually became a doctor on ABC's 2011 show Off The Map, set in a South American jungle clinic.
Grey's Anatomy's Shonda Rhimes helped create the TV show, with Henderson starring as Dr Ben Keeton. Though the show only lasted one season it's possibly the role helped Henderson land his recent Grey's part.
5. Secrets and Lies
Following Off The Map, Henderson found roles in movies The Moment and Devil's Knot,TV series Rake and New Zealand's Auckland Daze - cameoing as a version of himself.
In 2014 he found himself as a suspect in a murder case in the Australian drama Secrets and Lies. The six-part crime series earned Henderson a Logie Award nomination for Most Outstanding Actor.
So what's next?
Other than the announcement that he will be joining the cast of Grey's Anatomy for their 12th season, Henderson will also be starring with Jake Gyllenhaal, Keira Knightley, Jason Clarke and Josh Brolin in the disaster thriller Everest, set for release on September 17.
He will also star in the film Hellbent, which is in post-production, set to hit cinemas in 2016.