The couple obtained a marriage license Tuesday at a courthouse in Beverly Hills.
Harris called off the couple's previous engagement in June 2011, prompting Playboy to affix "runaway bride" stickers to an issue introducing her as Mrs. Hefner.
Celebrity website TMZ first reported the couple's license. It says they reunited earlier this year and plan to wed on New Year's Eve.
LA County Recorder Public Information Officer Elizabeth Knox says the license is valid for 90 days.
The Playboy founder has been married twice before. His spokeswoman Teri Thomerson didn't immediately return a message Tuesday.
(Copyright 2012 by The Associated Press. All Rights Reserved.)