Next Saturday's third Bledisloe Test against New Zealand was supposed to be the 34-year-old's last hurrah, but he has agreed to delay his retirement for the second time.
"Playing for Australia is something I have never taken for granted," Sharpe said. "As such, to be asked to continue beyond the deadline I had set for myself was both flattering but also a request that was very difficult to turn down."
The veteran lock originally planned to hang up the boots at the end of the Super Rugby season but agreed to play in the Rugby Championship after the Wallabies lost James Horwill (knee) and Dan Vickerman (retirement).
Sharpe was one of the Wallabies' best performers this season and was named captain after David Pocock and Will Genia were also struck down by the injury curse.
"To show the spirit and character that the team has is a mark of how the group has grown, both individually and collectively, and I have enjoyed playing my part in that," he added.
"The opportunity to lead the Wallabies again on what will be a challenging but exciting tour was too tempting. It is not easy to say no to your country."
Deans added: "Sharpey's presence and leadership has been a constant throughout the year - one of the few aspects of continuity that we've had through a season that is probably without precedent in terms of disruption.
"For that reason, it was straight forward asking him to continue, both following on from the June Tests when he had originally planned to retire, and then again following the Rugby Championship."
The 111-Test veteran will now call time on his career after the December 2 Test against Wales at Millennium Stadium. The Wallabies will also play France, England and Italy on their annual end-of-season tour.