Although not yet confirmed, it is believed Chapman may have had a heart attack, and doctors are now carrying out tests to determine what has happened.
The outlet reports that Dog might have to undergo corrective surgery.
The Blast reports that Dog is doing "fine" now, but remains in the hospital.
The 66-year-old's health scare comes just a few months after the death of Dog's wife Beth, who passed away on June 26 after battling throat cancer.
A spokesperson told the Mirror: "I can confirm Dog is under doctor's care and is resting comfortably. Thank you for all of your well wishes - keep 'em coming", Chapman's representative said.
"I would go, 'What do I want today, honey?' and she would name two things", he explained. "I really like to dream now". She'd be like, 'Let me do it, Big Daddy, you're too aggressive.' And then she became more aggressive than me.
PEOPLE confirms that the Dog's Most Wanted star has been hospitalized for a heart issue. The show chronicles Beth's battle. "I looked at the first show a little bit, but at that time, I wasn't able to handle it". He was also recently targeted in a check scam.