Willie Murray has admitted he never imagined the "little gangly boy from Dunblane" would grow up to be a champion.
"He's made history," Mr Murray said. "From a little gangly boy from Dunblane, it's just ridiculous.
"You saw him a few years ago, he had nothing on his bones, but he's worked very hard and that's what he's achieved. It's just incredible. I'm absolutely delighted."
Murray was one of the world's top juniors and won the US Open boys' singles title aged 17, but his dad did not expect anything like the success his son has gone on to have.
"You always want your children to do well, obviously," he said. "He was getting better and better but you just thought, 'Oh that's good' and moved on to the next tournament. It just grew from there.
"We never thought he was going to be terrific at it. We thought he was okay, but things improved as he got into the professional ranks."
Although Sunday's match was straight sets, it lasted more than three hours and there were plenty of tense moments.
Not least among those was the final game where Murray was 40-0 up only for Djokovic to fight back and force three break points before the Scot finally took his fourth match point.
There were no nerves from Willie, though, who said: "I was loving it.
"I just felt it was a great experience. You've got to embrace it. And I think on occasions like that, he's being trying so hard to embrace it and he's done it. It was fantastic."
It was an extra special moment for newsagent Willie, who was not in New York to see Andy lift the US Open trophy.
"I didn't make New York unfortunately but these things happen," he said. "I'd been to a few of them but it didn't happen for him the times I was there. But I've been here now and that's terrific. It's very special." Mum Judy is a more demonstrative presence in the Murray support camp and she revealed what was going through her mind as her son tried to win the dramatic final game.
She said: "I was thinking, normally when you're 40-0 up and serving, there's a very high chance you're going to win that game, and then suddenly he was a little bit tentative, which is totally understandable, and before you knew it it was deuce, and then Djokovic had the break points.
"Some of the points that they both played in that last game were just outrageous, and he just managed to keep his composure and get there in the end. It was a fantastic match and I'm absolutely thrilled for him."