UFC president Dana White confirmed the news to ESPN.com, following an initial report by Newsday. The bout will take place at UFC 169 at the Prudential Center in Newark, N.J.
The contest was to take place at UFC 167 in Las Vegas. According to a statement provided to Newsday, the UFC and Nevada State Athletic Commission agreed "a short postponement would allow both athletes more time to train for the bout."
Both fighters are coming off knockout losses in their most recent performances.
Mir (16-8) suffered a first-round TKO loss to Josh Barnett at UFC 164 on Aug. 31. The 34-year-old veteran protested an early stoppage in the fight, as it appeared he was still intelligently defending himself when referee Robert Hinds waved it off.
Nevertheless, Mir has dropped three consecutive fights for the first time in his 12-year career. He also was finished in the second round of a heavyweight title fight against Junior dos Santos in May 2012.
Overeem (36-13) suffered a knockout loss to Travis Browne at UFC Fight Night 26 on Aug. 17. After dominating the early moments of the fight, Overeem took a front kick to the chin late in the first round.
A former heavyweight champion in multiple promotions, Overeem is 1-2 since signing with the UFC in 2011. He's been knocked out in back-to-back fights.