"The wedding is off," Hefner, 85, tweeted Tuesday. "Crystal has had a change of heart."
Though the wedding was to take place Saturday, a heated weekend telephone argument between Hefner, 85, and his 25-year-old fiancee, who had been Miss December 2009, appears to have ruptured the nuptials, according to TMZ.com.
"After much deep reflection and thought I have decided to end my engagement with Hef," Harris wrote on her website Tuesday. "I have the utmost respect for Hef and wish him the best going forward. I hope the media will give each of us the privacy we deserve during this time."
More than 300 people had been invited to the big event, according to People.
But Hefner was taking the split in stride. Just hours after tweeting about the canceled wedding, he returned to Twitter to say: "Since we're not getting married on Saturday, I've scheduled a movie: 'Runaway Bride.' Seems appropriate."
This would have been Harris' first wedding.
Hefner has two children, Christie and David, with Mildred Williams, whom he divorced in 1959, six years after founding Playboy magazine. He subsequently had two sons, Marston and Cooper, with second wife Kimberly Conrad, 1989's Playmate of the Year. The couple separated in 1998, after nine years of marriage, and remained separated until filing for divorce in 2009 when their younger child turned 18.