The boxing great's family told The Philadelphia Inquirer that the 78-year-old was staying at a nursing home in Cherry Hill, and had been suffering from congestive heart failure and diabetes.
Born under the name Carmine Orlando Tilelli in Brooklyn, N.Y., Giardello started his professional boxing career after moving to Philadelphia in the late 1940s.
He defeated Joey Giambra, Gil Turner, Walter Cartier, Chico Vejar, Holley Mims, and Hall of Famers Billy Graham, Dick Tiger, and Sugar Ray Robinson on his march to the middleweight title. On Dec. 7, 1963, he took the championship with a 15-round decision over Tiger.
After a pair of non-title victories over Rocky Rivero, Giardello successfully defended his title against Rubin "Hurricane" Carter. He lost the title to Tiger in a 1965 rematch.
Giardello retired in 1967 with a pro record of 101-25-8, including 33 knockouts. He was elected into the International Boxing Hall of Fame in 1993.
The December 1964 fight between Giardello and Carter was part of the 1999 movie "The Hurricane" starring Denzel Washington, which told the story of how Carter served 19 years in prison after being convicted in 1967 of three murders. The conviction was later overturned.
It was the movie's depiction of the boxing match, which suggested that Giardello had won a unanimous decision unfairly, that sparked a federal defamation lawsuit from the former champ. He settled for undisclosed terms with Universal Pictures, Beacon Communications and Azoff Films.
"For 19 years, I fought the greatest fighters around and I beat Carter fair and square," Giardello told The Associated Press in 2000. "I just wanted to set the record straight, and I think it has been."