Merlin, who appears as a bartender on the hit Channel 4 dating show, has been told he has a 4.5cm Stage 3 tumour.
In an interview with The Mirror, Merlin told of how he started getting pain in June, but believed scar tissue in his stomach from a car accident some 26 years earlier was causing it.
The 46-year-old has been told he he has a 75% chance of living beyond five years and now faces a year of treatment.
“I thought, as most people must when they get a diagnosis, ‘Oh fuck, I’ve got cancer’,” he told the newspaper.
“I also wanted to know, what are my chances of surviving? It’s terrifying – of course I want to live.
“I’ve shed a tear in private. But you can choose ‘to do’ or ‘not to do’. I chose to lead my life as normal, to stick to the facts about it, and to keep putting one step in front of the other.”
He added: “I won’t let it get the better of me.”
Merlin revealed he has also been receiving support from his fellow First Dates stars, maître d’hôtel Fred Sirieix and waiters CiCi Coleman and Grant Urquhart.
Merlin made his first appearance on First Dates when the series launched in 2013, and has been a mixologist and bartender for more than 20 years.
He also owns of his own bar and restaurant, The Priory Tavern, in Kilburn, north-west London.