The 71-year-old passed away over the weekend in his Essex home with his family by his side.
But his wife - Linda, who starred on the show alongside him - has now revealed he was diagnosed with bowel cancer.
Despite an operation to remove the tumour, he was told he had only six months to live but died just days later - she told The Sun.
Also, Linda told how her husband had lost six stone from dieting during lockdown.
“Pete was a lovely man and I was so lucky to have him for 25 years,” she told the paper.
“I said to him, ‘We’ve not only been 25 years, it’s been day and night with each other.’ He was my life.
“I have a message from a young lad I know who said, ‘Ordinary people won’t be remembered, but we’ll remember Pete forever - like the pyramids.’ I thought that was beautiful,” she added.
Pete and Linda and their son George Gilbey became household names in 2013 after joining the hit show.
They left in 2014 before returning to the show in 2016 and becoming fan favourites ever since.
A statement issued on behalf of the family by Channel 4 said: “We are deeply saddened to announce that Gogglebox star Pete McGarry passed away at the age of 71 this weekend with his family by his side after a short illness.”
The statement added: “Pete will be dearly missed by the entire Gogglebox family, cast and crew.
“Our thoughts are with Linda, their children and grandchildren.
“Since 2000, Pete and Linda have fostered over 100 children and he is a beloved father, husband and grandfather. The family have asked for privacy at this sad time.”