Glenwood authorities said firefighters were called to the 900-block of East 194th Street around 5 p.m.
The fire had fully engulfed a condo on the second floor of a three-story building when firefighters arrived, officials said.
The medical examiner's office identified the man who died as 64-year-old Frankie Thomas, who lived in the building.
Officials said the investigation is active.
Neighbors in adjoining condos in the building were displaced, and officials contacted the Red Cross for assistance.
Officials said they expect to release more information on Sunday.