It was revealed last year that the Britain's Got Talent winner was joining the cast of the BBC drama as new student Kyle Stack. Sampson will make his on-screen debut when the show returns from a break next week.
"I'd done bits here and there. I'd trained as an actor, but not done anything on screen," he told What's On TV. "StreetDance was the biggest thing I'd been a part of before Waterloo Road."
Asked if he had watched his episodes yet, he said: "No, not yet. I'm not sure I want to, I feel a bit nervous!"
The 17-year-old went on to praise the show's "welcoming" cast.
"Normally, in my other jobs, I turn up, work for the day and then leave," he said. "Waterloo Road is different as you see everyone every day for months and become friends. Everyone in the cast and crew are lovely."
Waterloo Road returns on February 2 at 8pm on BBC One.
> Sampson 'likes acting more than dancing'