Duncan's publicist Joy Fehily said the 54-year-old actor is in stable condition and is expected to make a full recovery. He is being treated at a Los Angeles-area hospital.
Fehily wouldn't confirm a TMZ.com report that Duncan's actress-girlfriend, Omarosa Manigault-Stallworth, discovered the former bodyguard in distress at about 2 a.m. in his home and revived him by performing CPR.
Duncan is best known for his performance in the 1999 prison drama "The Green Mile," starring Tom Hanks. The actor has also appeared in "Armageddon," "The Scorpion King," and "Sin City."
The Associated Press contributed to this report.