The former couple - who initially announced their engagement in December 2010 - announced that they were cancelling the nuptials last week just days before the ceremony when Harris experienced a "change of heart".
While Hefner later described the split as a "heartbreaker" and claimed that he didn't see the break-up coming, the 85-year-old has since claimed that he and 25-year-old Harris remain friends.
"Crystal came by to see how I've been doing," Hefner wrote on his Twitter page on Sunday. "We remain close friends."
Hefner went on to reveal that Harris returned the couple's dog Charlie to the Playboy mansion, adding: "I appreciate it, because I really missed him."
Harris was recently blasted by Hefner's ex-girlfriend Holly Madison for partying at a Las Vegas pool party with Heidi Montag on what would have been her wedding day.
Hefner is said to have taken up a romance with current Playboy 'Miss January' Anna Sophia Berglund since splitting from Harris.