Speaking on BBC Radio 4, the 78-year-old actor also said that he licked the newborn’s face afterwards.
Presenter Libby Purves appeared surprised by the admission and challenged aspects of it, but the Yorkshireman insisted he had seen his mother deliver babies.
The birth took place in 1963 when Blessed was best known for playing Pc Fancy Smith in popular BBC police series Z-Cars.
Talking about the incident, he said: “I rushed across to her and she was having the baby and had her legs open. She knew me in Z-Cars. She said ‘please Mr Blessed, I’m having a baby’. I said ‘breathe deeply’ and gradually I got the baby out.”
The Mexborough-born star continued: “I delivered it in Richmond Park and the afterbirth came out, and the clots, I got rid of the clots. Then I got the afterbirth out, then I bit it loose then I tied it into a knot, and then I just called for help and eventually an ambulance came.”
The Flash Gordon star recalled that he was covered in blood.
“I was wrapping her, wiping her... And I was licking the baby’s face,” he said.
Following the interview, Blessed trended on Twitter. Some users posted tweets of amazement at what they’d heard: @Two_Tents wrote: “I hope Brian Blessed didn’t bite off more than he could chew when he delivered that baby.”
Another from @jubo85 said: “Nothing worse than reading about Brian Blessed chewing an umbilical cord and afterbirth, whilst eating lunch #boak.”
Other users of the social media site were relieved to discover the reason the veteran actor was trending was not due to his death.
Typical of many was this from @PeteJLewis: “Seeing Brian Blessed trending had me all worried, but luckily he’s still alive and still incredible.”
There were also humorous tweets as this one from @Onewheelsteve demonstrates: “I saw that Brian Blessed is trending and my heart sank. Thankfully our great British institution is alive and well and licking babies’ faces.”
Blessed will be making an appearance during Book Week Scotland 2015, which runs from November 23 to 29.