The couple are engaged for a second time and plan to walk down the aisle on New Year's Eve, according to E! News.
Hefner's rep was unable to confirm the report to ABCNews.com.
But Harris recently hinted on Twitter that she was ready to say, "I do."
"Dear past, thank you for all the lessons. Dear future, I'm ready," she tweeted.
Hefner, 86, and Harris, 26, were initially due to marry in June 2011 before more than 300 guests, but she called it off days before the wedding.
"I called it off because I didn't think it was the right thing for me to do," Harris told TV-host Ryan Seacrest at the time. "It was mutual between Hef and I. There was no fight. We sat down and we talked about it."
"Hef's lifestyle isn't the most normal lifestyle," she said. "That's the thing. This isn't the lifestyle for me, the multiple girls all around. It's not the lifestyle I wanted."
It appears the couple have worked things out. Harris announced in June that they were back together after rumors that she had moved back into the Playboy mansion.
"Yes @hughhefner and I are back together. Yes I am his #1 girl again. Yes we are happy. Hope that clears up any confusion! xo," Harris tweeted in June.
The rescheduled wedding service is set to be "an intimate gathering with close friends and family" at the Playboy mansion, according to TMZ.
It will be Harris' first marriage and Hefner's third.