The 19-year-old Hollywood star says she developed trust issues and a "slight case of PTSD" because of this, reported Glamour magazine.
The star's father left before she turned 13, and her mother raised her and her four brothers as a single parent.
"I was 12. It was a pretty bad experience. It could have rocked our family and messed us up, but it actually made us a lot tighter. My brothers bumped up into the roles of fathers and kept me in a bubble where I could live in a world that wasn't jaded and ruined," she said while talking about her parents divorce.
"I don't think I will truly find a way to forgive. The things that he did are unforgivable... My forgiveness is that I'm living my life."
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The actress says she finds it hard to trust people because of her father's walking away.
"In my business in general, it's hard to trust people. And it definitely affected me at a young age in terms of accepting people into my life on a personal level," Moretz revealed.
"But I've overcome that in the past few years - dealing with relationships, dealing with guys. You don't realize why you're acting a certain way, and then you start to piece it together, and you realize you've got a slight case of PTSD.