Harris claimed the couple only had one brief sexual encounter during their two years of dating.
"[It lasted] like about two seconds," Harris told Howard Stern during a Tuesday appearance on his SiriusXM radio show.
According to the 25-year-old former Playboy Playmate -- who got engaged to Hefner over the holidays last December but called off her wedding in June just days before she was set to walk down the aisle -- she never even saw the 85-year-old Playboy founder and editor-in-chief nude.
"Hef doesn't really take off his clothes. I have never seen him naked," Harris said laughing.
She added that she was never really interested in having a physical relationship with Hefner to begin with.
"I was over it. I just like, walked away. I am not turned on by Hef. Sorry," Harris explained.
However, Harris insisted her feelings for Hefner were real, while she also enjoyed living in the Playboy mansion.
"I loved [Hefner] and the lifestyle," the former reality TV star said, adding she thought marrying him was what she wanted at the time until the idea of staying with him for just a couple days longer repelled her.
Now that Harris has split from Hefner, she said she's unsure of what to do with her newfound freedom.
"It's scary. It was so sheltered that now I'm like, 'What do I do?'" Harris told Stern.