The actor has been on set at the show's base in Greenock, Scotland this week, reprising his role as Kyle Stack for a single episode.
Kyle was arrested at the end of series seven for a serious assault on Josh Stevenson with a crossbow.
The bad boy's return storyline will see him make his way to Waterloo Road's new Scottish home after being released from prison. However, further plot details are being kept under wraps for now.
Sampson commented: "It's great to be back, especially for such an exciting new adventure and an incredible storyline - but I'm not saying what happens! I'm looking forward to getting going - new cast, new crew, new set - it's going to be great!"
Waterloo Road's executive producer Cameron Roach added: "In recent years Kyle Stack has been one of our most popular characters. It made sense to follow his release from prison and to continue his story.
"We're really looking forward to welcoming George back and for him to be part of the series in Scotland. We know loyal fans of the show will be captivated by his return story - it will certainly be memorable."
Waterloo Road is currently airing series 8B on Thursday nights on BBC One, while Kyle's return will be part of the next set of episodes later this year.