The millionaire businessman, 63, fell ill earlier today (October 1) while at work in Darlington. He was taken to hospital to undergo a series of tests.
Bannatyne has since tweeted: "In hospital attached to a few wires feeling tired but am sure I will be discharged tomorrow fit & well (fit a pensioner can be anyway).
"Today was my first trip inside an ambulance & with siren wailing. Hope it is the last. LOL."
A spokesperson for The Bannatyne Group said: "Everyone at the company is very concerned and upset but we know that Duncan is a very strong person and we are confident he will make a full recovery.
"Everyone wishes him well. We'd like to thank the quick and professional actions of the paramedics who attended to Duncan and thank the staff at the Memorial Hospital for his ongoing care."
The official Twitter account for Dragons' Den also wished him a speedy recovery.