Gregg Popovich's side bounced back from their defeat in the Finals to the Heat in 2013 to claim the title, as they beat Erik Spoelstra's men 104-87 in game five to take the series 4-1.
The 38-year-old admitted that this success was more important to him than his other four title wins, due to his advancing years and also having his family around him to celebrate the triumph.
Duncan told USA Today: "Very special. To do it at home, to do it with my kids and my family and my friends here made it so much more special. Just a great experience, and a great experience for them.
"For whatever reason, it is sweeter than any other, whether it be because of the time frame, because I'm coming towards the end of my career, because I can have these two [daughter Sydney and son Draven] here and really remember it and enjoy the experience, all of those things make it that much more special."
Duncan scored 14 points in game five to fire his side to victory.