The 'Can't Get Used To Losing You' singer announced his diagnosis while performing at the Moon River Theatre in Branson, MO over the weekend.
Williams said that he's determined not to let the diagnosis slow him down and promised that he'd continue to perform.
"I do have cancer of the bladder, but that is no longer a death sentence," Tri-Lakes News quotes him as saying.
Williams continued: "People with cancer are getting through this thing. They're kicking it, and they're winning more and more every year. And I'm going to be one of them."
The singer will reportedly soon begin treatment, which could cause him to miss his annual series of holiday concerts.
Williams vowed to return for next year's festive shows to celebrate his 75th year in show business, saying: "I'm going to do the shows I've planned to do."
He has scored numerous popular singles over his recording career, including the number one hit 'Butterfly' as well as the top 10 tracks 'Lonely Street' and 'Canadian Sunset'.
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Watch Andy Williams sing the theme from Love Story below: