"Mamma Mia!" has been extended through Jan. 4, 2009 at Mandalay Bay, the cast was told late Saturday.
The show was scheduled to close this summer.
Already the longest playing Broadway show on the Strip, "Mamma Mia!" marks its fifth anniversary on Feb. 13.
The feature film adaptation will be released this summer, with Meryl Streep leads an all-star cast featuring Pierce Brosnan, Colin Firth, Stellan Skarsgård, Christine Baranski, Julie Walters, Amanda Seyfried and Dominic Cooper.