Alongside his brother Thomas Duff, he co-owns Southern Tire Mart, the nation's largest truck tire dealer and retread manufacturer, and Duff Capital Investors, the largest privately owned business in Mississippi.
Duff graduated from Columbia Academy and later attended Utah Valley University, where he studied business.
James’s father, Ernest Duff, founded Southern Tire Mart in 1973.
James and his brother Thomas both worked there as teenagers and assumed control of the struggling company in 1983.
[2] James and Thomas co-founded Duff Capital Investors, a holding company with total revenues exceeding $5 billion.