The pair's hit revue was supposed to run for just six weeks back in 2008, but it has been pulling in fans for well over a decade - and now the siblings have decided it's time to end the show.
The curtain will come down on the act in November.
Making the announcement on "Good Morning America" on Thursday, March 21, Donny said, "It's official. It's very hard to say."
And his sister admitted it will be tough to say goodbye to the fans.
"They've come from all over the world to see us here in Vegas," she explained.
And Donny paid tribute to his sister, revealing the show has helped her through "so much" over the last 11 years, adding, "She gets onstage and she's such a professional and she does a great job. I'm gonna miss this a lot."
Fighting back tears, an emotional Marie said, "He's been my rock. I went through a terrible divorce here and a terrible custody battle and I lost a child here."
She insisted the show helped the brother and sister act for a bond that will never be broken, adding, "I will never let anybody hurt him."
As for the last show, Donny plans to have "the time of my life," adding, "It's the end of the 'Donny & Marie Show'; it's not the end of Donny & Marie."
The final show will take place on November 16 and Marie revealed she plans to take on some acting work after the Vegas run ends.