His family says Cardillo, who was born in Guelph, Ont., on Oct. 26, 1930, died early Sunday.
Cardillo began his career in municipal politics in 1963, and served 20 years as alderman before being elected as mayor in 1983.
He served 12 years as mayor, until his retirement in 1994.
Cardillo was the longest-serving mayor at the time, now only surpassed by current Mayor Carl Zehr.
Zehr says Cardillo was so proud of his city, he would stop to pick up garbage and litter.
Cardillo was "very helpful, and would take the shirt off his back" for anybody, Zehr said Sunday.
"Everybody knew Dom. It was by first name alone. His reputation as a kind, gentle individual was his primary legacy."
Merv Villemair served on council with Cardillo for 15 years — eight of those years on regional council.
"Honesty was all over him," Villemair said, adding that Cardillo was a great promoter for Kitchener, and for attracting business.