The sports icon was recovering after undergoing recent surgery to fix a stomach condition when he passed away on Thursday (25Oct12).
Reports suggest he was also battling colon cancer.
The revered trainer and commentator helped Thomas Hearns and Jimmy Paul land world championships in the 1980s, and in recent years he had worked with world heavyweight champion Wladimir Klitschko and middleweight sensation Andy Lee.
He was also a beloved fight commentator and a former bantamweight champion in the early 1960s. Steward was inducted into the International Boxing Hall of Fame in 1997.
Paying tribute to his late trainer, Klitschko says, "Boxing has suffered a tremendous loss... (Brother) Vitali and I, along with the entire Team Klitschko, send our deepest and most heartfelt condolences to Emanuel's family and friends. It is not often that a person in any line of work gets a chance to work with a legend. Well I was privileged enough to work with one for almost a decade. I will miss our time together."