Lionel Adams, 59, told the Calgary Sun his 8-year-old orange tabby called Tiger began some unusual behavior late last summer.
"He would climb into bed and take his paw and drag it down my left side -- he was adamant there was something there," Adams told the Sun. "And it was right where the cancer was."
Surgeons subsequently removed a tumor the size of a soda can, he said.
"I think if he hadn't done the pawing part it could have gone on for another five, six months undetected," he said.
Barbara Walmer, department head of behavior at the Calgary Humane Society, told the newspaper there is evidence some dogs can sniff out some cancers and it's feasible cats, with their acute olfactory sense, could do the same.
"I think we see more predicting in dogs but, for sure, many pet owners have reported pets can have a sixth sense when knowing when something is wrong," she said.