The 25-year-old was due to marry the Playboy founder in a ceremony at the Playboy Mansion on June 18 but just four days before the news of their split came when Hefner posted a message on his Twitter page.
Harris later took to her official website to confirm the news.
She said: 'After much deep reflection and thought I have decided to end my engagement with Hef.
'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.'