Rob Barty says he never thought Ash would play tennis again after she quit the sport for a stint in cricket.
When the 23-year-old walked away from tennis five years ago her parents supported her decision.
But Rob didn’t think she’d come back at all, let alone win a grand slam.
"When she quit I never for one moment though she would go back to tennis," he told ABC Radio on Wednesday.
"We never raised it with her during her time off.
“It wasn't until one day I came home and found about four boxes of new tennis balls at the front door.
"It was Ash deciding she was going back to play tennis and away she went."
Rob thought it was exciting when his daughter cracked the top 100 in women's tennis, now she is world No.2.
"She sent me a text when she cracked the top 100 and said 'Hey dad, finally made it. I'm in the Top 100’.
"I can remember speaking to my wife Josie about it and saying I wonder if Ash will ever be as good to be seeded in a grand slam event as in top 32.
"Now here we are 12-18 months later she's No.2 in the world and she's won a grand slam."
He said the win felt "pretty surreal" with the Queenslander the first Australian to win the French Open since Margaret Court in 1973.
Rob and Josie didn't make it to France in time for their daughter's game but have since caught up with her and her coach Craig Tyzzer for a round of golf.
"They were both very, very happy, very pleased with themselves, but quite exhausted to be honest," he said.