Mariska Hargitay will never forget the moment she discovered her biological dad — or the heartbreaking way she found out.

The actress recalled “being invited to this guy’s house,” explaining on Wednesday’s “Call Her Daddy” podcast that the “lovely” and “obsessed” man was head of her late mother Jayne Mansfield‘s fan club.

The “Law & Order: Special Victims Unit” star, 61, went to see his “overwhelming” and “huge” collection “of memorabilia and movie posters and everything related to” the movie star, who died in 1967 at age 34.

Then, the superfan asked, “Do you want to see a picture of Nelson [Sardelli]?’”

Hargitay remembered a “jolt” in her body as she asked, “Who’s Nelson?”

She “knew [the truth] in one second,” thanks to “millions of … little fragments of a memory, of a moment, things [she] caught that went into [her] subconscious.”

The man “sort of panicked and turned white” before saying, “Oh, it’s probably not true.”

Hargitay noted, “I think that he couldn’t believe that I didn’t know. I was 25, how could I not know? … He showed me [Sardelli’s] picture and on a cellular level, it was just DNA talking to DNA. I knew it was true.”

The Emmy winner felt as if her “life was over,” describing how the “rough” revelation broke her identity “in two.”

She said, “It was like I had thousand pellets of hard truth going, ‘My brothers aren’t my brothers. I’m not related to all my family that I grew up with in Hungary. What about this? What about that? … Oh, my gosh, all the times … everyone asked me if I was Italian my entire childhood.’”

Hargitay felt “barraged” with a “million missiles of these mini micro moments.”

After a “confusing” visit with her brother — who also didn’t know the secret — she drove “hysterically crying” and “disassociated” to her dad Mickey Hargitay to confront him.

He denied the bombshell, asking, “What? What are you talking about? That’s crazy. That’s so not true. You look like my father, exactly like my father. You are a Hargitay to the end.”

In that “extraordinarily painful” and “visceral” moment, Mariska decided to “pretend to believe” Mickey and “became an adult.”

She explained, “I was in so much pain, so overwhelmed and then looking at this man who has been nothing but loving to me and nothing but this amazing father to me.

“I saw his pain and I said, ‘It doesn’t matter what I feel. I love him. We’re done here.’ And so I said, ‘OK, thank you for telling me’ … and we never spoke of it again.”

Mariska now understands why Mickey, who passed away in 2006, reacted the way he did as the mother of two adopted children herself — Amaya and Andrew.

“They are no different from my biological son,” she said, referencing 18-year-old August.

Mariska shared the secret publicly in “My Mom Jayne,” which premiered out last month — and was attended by Sardelli.

In the May documentary, she said finding out about her paternity was like the “floor [falling] out underneath” her and her “infrastructure dissolv[ing].”.”