Hefner, who has married twice before, is set to exchange vows with Harris in a small ceremony New Year's Eve at the Playboy Mansion.
Time will tell if third time's a charm for the Playboy mogul as Harris has left Hefner at the altar before.
Just five days before their planned wedding last summer, Harris got cold feet and called off their engagement.
The playmate is 25 years old, 60 years younger than Hefner.
The couple has been engaged for two years.