The 50-year-old businessman and the "Without You" hitmaker started dating in 2015 and broke up in October next year - barely nine months after they announced their engagement.
"I was at a low point in my personal life. She was kind, exciting and fun. Mariah is a woman of substance. But it was a mistake for her and a mistake for me," Packer tells Weekend Australia magazine.
The investor, however, adds that he blames himself for failing at his marriage with former wife Erica, with whom he shares three children - daughters Indigo (nine) and Emmanuelle (five), and son Jackson (seven).
He was also married to model Jodhi Meares.