Grady Allen was hospitalized last week with heart problems.
"The organization wishes to extend its most sincere condolences to Coach and his entire family," the Raiders said through their Twitter account.
Dennis Allen plans to return Wednesday in time to coach Oakland against the Denver Broncos on Thursday night.
Allen, who was the Broncos' defensive coordinator last season, has guided the Raiders to a 3-9 mark in his first year with the squad.
