The boy was born on the bathroom floor of his home in Gloucestershire in the south-west of England at around 6pm, after “arriving very quickly”.
“I was running to the gym, grabbing a mat, going into the bathroom, grabbing the mat on the floor, towels down, arm, arm, arm,” Tindall said.
The baby, named Lucas Philip, weighed 8 pounds 4 oz at birth, a spokesman for the couple told CNN.
The couple’s other two children, Mia Grace and Lena Elizabeth, were not home Sunday for the new arrival, but they have seen him ever since and are “on the moon,” Mike Tindall said.
The midwife, who was supposed to find them at the hospital, was quickly at the scene because she was not far away, and a second arrived “when her head arrived,” she added.
Queen Elizabeth and her husband, the Duke of Edinburgh, are “delighted with the news” and look forward to seeing the new addition to the family when “circumstances allow,” a Buckingham Palace spokesman told CNN.
Zara feels healthy, Tindall said, and has been walking with the baby.
“She was a warrior, as always, they always are,” Tindall said. “We can never judge a woman as to what they have to go through during childbirth.”
He said there were advantages to giving birth at home. After Lucas arrived, Tindall watched an old game of rugby and a bit of golf with his new son.
Zara Tindall is an equestrian who has won a silver medal in a team event at the 2012 London Olympics.
She met her future husband during the 2003 Rugby World Cup while playing in England. The couple married in Edinburgh in 2011.
CNN’s Amy Cassidy contributed to this report.