Born in Detroit, Michigan, to Sam and Jenny Harris, he moved to London, Ontario, when he was a few months old.
Harris attended St. George's School and Central Collegiate Institute before receiving a Bachelor of Commerce degree from the University of Toronto in 1949.
After his father suffered a heart attack, Harris took over the day-to-day operation of his family's metals trading business established by his great-grandfather in 1886.
In 1986 he was made an Officer of the Order of Canada in recognition for having "devoted his energies to community service at various levels, endeavouring to improve the quality of life for all Canadians".
Milton Harris died in 2005 of abdominal cancer in Toronto, aged 77.