Holly Madison, Kendra Wilkinson and Bridget Marquardt have all sent messages of support to Hefner over Twitter.
"Just stopped by the mansion 2 give @hughhefner a hug. He seems to be handling this well. He even had a sense of humour about it! #LoveUHef (sic)" wrote Marquardt.
She later added: "I feel bad 4 Hef & I wanted him 2 know that I'm here 4 him."
Hefner confirmed the visit on his own Twitter feed, saying: "Bridget Marquardt came by to give me her loving support. Very dear."
The 85-year-old also told followers that his ex-wife Kim Conrad and her mother had visited the Playboy Mansion to "to lend their emotional support", which he "appreciated".
Las Vegas-based Madison, who appeared alongside Marquardt and Wilkinson in the Playboy Mansion-based The Girls Next Door, retweeted a message of support to Hefner from Wilkinson, adding: "U r too sweet. Wish I was there to support, too!"
Hefner confirmed that his engagement to 25-year-old model Harris had ended yesterday, just days before they were scheduled to tie the knot at the Playboy Mansion.
"The wedding is off," he told Twitter followers. "Crystal has had a change of heart."
Playboy Playmate Harris later issued her own statement, saying: "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."
Twice-married Hefner announced plans to wed Harris on Christmas Day.