Trevaldwyn began his career by posting comedic videos online, showcasing his versatility through a range of original characters. His growing popularity led to breakout roles in 2022, beginning with The Bubble on Netflix, where he played the quirky character Gunther. That same year, he portrayed Ollie Rogers in Ten Percent, the English adaptation of the French hit Call My Agent!, which premiered on Amazon Prime in April. Shortly after, Channel 4 announced that Trevaldwyn would not only star in but also write Billi, an original comedy that aired in May 2022, further establishing his creative talents both in front of and behind the camera.

In February 2023, Trevaldwyn made a notable appearance as a guest presenter at the Casting Director’s Guild Casting Awards, reflecting his growing recognition within the entertainment industry. Meanwhile, his film career continued to expand with a role in Sweet Sue, a project currently in post-production that features Maggie O’Neill, Tony Pitts, and Hannah Walters. These roles underscored his dynamic range and ability to contribute meaningfully to both television and film.

2024 marked another pivotal year for Trevaldwyn, beginning with his casting as Tuffnut Thorston in the live-action remake of How to Train Your Dragon, an eagerly anticipated project announced in January. In May, he appeared as Stan in the third series of the popular BBC comedy The Outlaws, featuring in four episodes. Most recently, in July 2024, Trevaldwyn took on the role of Jedi Mog Adana in an episode of The Acolyte, adding a sci-fi credit to his growing and diverse body of work.