According to BBC, Steve Green from talent agency Artists International Management Inc confirmed that Sledge died at his home in Baton Rouge, Louisiana, on Tuesday.
"He was one of my first acts, he was a terrific person and you don't find that in this business very often," said Green. "He was truly a standout."
Sledge had surgery for liver cancer in January 2014 but soon resumed touring. BBC reports.
Sledge's debut single When a Man Loves a Woman reached the top 10 twice in the UK and topped the US Billboard chart for two weeks in 1966, when it also got to number four in the UK chart.
According to BBC reports, before his music career, Sledge worked in the cotton fields around his hometown of Leighton in northwest Alabama, before taking a job as a hospital nurse in the early 1960s.
A patient heard him singing while he worked and recommended him to record producer Quin Ivy.
The singer was inducted into the Rock and Roll Hall of Fame in 2005 and was a member of the Alabama Music Hall of Fame and the Louisiana Music Hall of Fame.
Sledge is survived by his wife and children.