Murray's support team, including Judy, girlfriend Kim Sears, best friend and hitting partner Dani Vallverdu, physio Andy Ireland and physical trainer Jez Green, have watched him come so close before on so many occasions.
At Wimbledon nine weeks ago, they shared his tears on Centre Court as the 25-year-old lost to Roger Federer in the final, and four weeks later they celebrated with him in the same box after he won Olympic gold.
On Monday night in New York there were tears again, but this time of joy, as Murray beat Novak Djokovic over five tense and brutal sets to finally land one of the four biggest prizes in tennis.
Mother Judy said: "He's been dreaming of winning a grand slam since he was little and it's been his goal since he became a full-time player, that's all he's talked about.
"He's obviously come close on a number of occasions and not quite been able to do it and I think winning the gold at the Olympics gave him the belief that he could get through a major final.
"To see him do it was fantastic. I probably know better than anybody how hard he's worked over how long a time and I know much it means to him, so it was great to be able to see him get what he deserved."
As Fed Cup captain and an important figure within British tennis, Judy is able to support her son at the biggest tournaments, but new champion Murray was keen to stress how important the backing from his whole family has been in his success.
He said: "It's not just my mum, the rest of my family has always been there as well. Both my parents made a lot of sacrifices to give me and Jamie the opportunity to play tennis so it's nice in a way to repay them for all those sacrifices.
"Family's the most important thing and they've given me a lot of help, especially when I needed it after Wimbledon and tough moments in my career."