During a discussion on the subject with actress/author Justine Bateman, "The Matrix" vet said she initially disregarded the notion that a woman's career in the business shifts in correlation to her age.
"I had heard that at 40 everything changed," said Moss, according to The Hollywood Reporter. "I didn't believe in that because I don't believe in just jumping on a thought system that I don't really align with."
"But literally the day after my 40th birthday, I was reading a script that had come to me and I was talking to my manager about it. She was like, 'Oh, no, no, no, it's not that role [you're reading for], it's the grandmother."
"I may be exaggerating a bit, but it happened overnight," added the star, now 53. "I went from being a girl to the mother to beyond the mother."
She emphasized how ageism is difficult to process as her male counterparts don't have the same pressure to appear youthful.
"It's a stereotypical story, working with men that are so much older and aging," she explained. "And people are enjoying the aging of them. While I'm much younger than they are."
Witnessing herself aging on the silver screen was dubbed "kind of brutal" for the mother of three.
"You don't feel like you've aged much and suddenly you're seeing yourself onscreen," she said. "I would look at these French and European actresses and they just had something about them that felt so confident in their own skin. I couldn't wait to be that. I strive for that. It's not easy being in this business. There's a lot of external pressure."