Mariska Hargitay opened up about a shocking secret she’s held for more than 30 years in her “My Mom Jayne” documentary.

The “Law & Order: Special Victims Unit” star revealed that Mickey Hargitay, who many have believed to be her father, is not her biological parent and that Italian singer Nelson Sardelli is her real dad.

“He was my everything, my idol. He loved me so much, and I knew it,” she told Vanity Fair of her upbringing with Mickey.

“I also knew something else. I just didn’t know what I knew.”

The truth of Mariska’s paternity led her down a rabbit hole because she felt she was “living a lie [her] entire life.”

Mariska’s mom, Jayne Mansfield, filed for divorce from Mickey in 1963. The late Playboy playmate then struck up a widely publicized romance with the singer and soon found herself pregnant with Mariska.

Months before she gave birth to the actress in 1964, Mansfield reconciled with Mickey. The Golden Globe winner, 61, said she found out the truth about her real father when she saw a picture of Sardelli.

“It was like the floor fell out from underneath me,” she recalled in the documentary, which will become available for streaming on HBO Max on June 27.

“Like my infrastructure dissolved.”

However, her dad, Mickey, denied the story when she confronted him.

At age 30, Mariska went to see Sardelli, now 90, in concert in Atlantic City, where she approached the Brazilian-born crooner.

“I’ve been waiting 30 years for this moment. I went full Olivia Benson on him,” she said, referring to her famous “Law & Order: SVU” character.

“I was like, ‘I don’t want anything, I don’t need anything from you … I have a dad,’” she recalled to Vanity Fair. “There was something about loyalty. I wanted to be loyal to Mickey.”

“I grew up where I was supposed to, and I do know that everyone made the best choice for me,” she said. “I’m Mickey Hargitay’s daughter — that is not a lie.”

Mariska explained to the outlet that the documentary was “kind of a love letter to [Mickey], because there’s no one that I was closer to on this planet.”

The “Lake Placid” actress, who shares three kids with husband Peter Hermann, pointed out that two of her children are adopted.

“They are my kids. Now I understand so much, and, boy, is it sweet,” she declared.

Mansfield died in June 1967 at age 34. Mickey passed away in 2006 at the age of 80.