Fox, 58, was being kept at the hospital "for testing and further observation," the Broncos said in a statement. "Our medical staff is currently in contact with Coach Fox, his family and the doctors who are treating him.
"Additional information will be provided as it becomes available."
ESPN reported the Broncos coach experienced chest pains while on the course and was taken to the medical center via an ambulance.
The broadcaster said his condition was not believed to be life-threatening.
The 7-1 Broncos are on their bye week.
Fox coached the Carolina Panthers for nine seasons before being hired by the Broncos in 2012. He led them to a 13-3 mark and the top seed in the AFC playoffs during his first year in Denver.