Paramedics revived Jackson before taking him to the hospital.
Brian Oxman, a Jackson family attorney, said he was told by brother Randy Jackson that Michael Jackson collapsed at his home in west Los Angeles Thursday morning.
Family members were told of the situation and were either at the hospital or en route.
Fire Capt. Steve Ruda told CNN a 911 call came in from a west Los Angeles residence at 12:21 p.m.
Ruda said Jackson was treated and transferred to the UCLA Medical Center.
Asked specifics of the patient's condition, he said he could not discuss them because of federal privacy laws.
The music icon from Gary, Indiana, is known as the "King of Pop."
Jackson is the seventh of nine children in a well-known musical family.