The formerThe Girls Next Door star and Hefner are set to wed at the Playboy Mansion on New Year's Eve in front of close friends and family, TMZ reported.
Harris reportedly moved back into the 85-year-old Playboy founder and editor-in-chief's mansion earlier this year. Once they reunited, the couple allegedly worked things out and came to the conclusion they should officially tie the knot.
According to the website, Harris needed a break from her relationship with Hefner to gain some independence before settling down and getting married.
Hefner was unsuccessful with his first two marriages to Mildred Williams, who he divorced in 1959, and to former Playmate Kimberly Conrad -- who he has been separated from for almost 20 years but only formally divorced in 2009.
The two failed relationships resulted in Hefner's hesitation to wed again, especially with ex-fiancee Holly Madison, causing the couple to split in late 2008.
Hefner originally planned to take things slow with 26-year-old Harris -- who was December 2009's Playboy Playmate -- after Madison had left him in the hopes of having a different outcome.