The playmate, 25, called off the nuptials on Tuesday, just days before they were to tie the knot Saturday at the Playboy Mansion.
"The wedding is off," Hefner Tweeted. "Crystal has had a change of heart."
More than 300 people had been invited – via Papeterie custom-made invitations – to their big day, which called for a pink Romona Keveza gown and Torrance Bakery strawberry cake.