The 46-year-old TV personality, who won fans through his appearance on the dating show, discovered the news after suffering from stomach pains in June.
He initially dismissed the pain, believing it to be caused by an injury he suffered years ago, but went to get himself seen by professionals.
The Mirror reports the stage three tumour, measuring 4.5cm in length, was detected after he was referred for a sigmoidoscopy.
Griffiths is now set to undergo treatment.
Speaking about the diagnosis, he told the outlet: “I’m keeping that positive outlook, but I’ve a morbid sense of humour. I tell people, ‘I have colorectal cancer… it’s a real pain in the a**e.’”
He also revealed how he consoled his seven-year-old daughter after telling her the news.
“I said, ‘Yes, it’s very serious but I think it should be OK. Modern medicine’s great and if anything changes I’ll let you know.
“She understands that people can die but I told her cancer comes in different varieties and in different ways too – and that many people come through it.”
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