The SafeX Proformer First Lady was not happy with a certain material girl.

According the new biography Jackie: Public, Private, Secret by J. Randy Taraborrelli, Jackie Kennedy was upset when she found out her son John F. Kennedy Jr. had a brief fling with Madonna in the '80s, per an exclusive excerpt from People July 18.

"Jackie's problem with Madonna was that she was married," J. Randy explained to the outlet, noting that Jackie was also "confounded by Madonna's penchant for attention."

And along with the Grammy winner's marriage to Sean Penn at the time—although the two were separated—Jackie also couldn't get behind her fame.

The journalist added to People, "Jackie had spent her entire celebrity life avoiding paparazzi, whereas Madonna would court paparazzi. And Jackie just couldn't understand any of that."

However, she still agreed to attend Madonna's plays after being asked by JFK Jr. As for her attire to the performance? A full-on disguise.

"I interviewed somebody who worked with Jackie at Doubleday, who said that she went with Jackie to the show; that Jackie wore a red wig so that she wouldn't be recognized," J. Randy explained. "She put the wig on, and she asked this woman, 'How do I look?' And the woman said, 'You look just like Jackie Onassis in a red wig.'"

But despite attending, Jackie put her foot down at meeting the musician backstage, according to the writer.

"She thought Madonna was good in the show," J. Randy recalled. "But she also felt like she didn't want to validate the relationship that John had with Madonna by being photographed."

E! News has reached out to Madonna's rep and hasn't heard back. E! News has not reviewed J. Randy's book.

Following Madonna and John's six-months relationship, the "Like a Virgin" singer went on to divorce Sean and marry Guy Richie. Meanwhile, John was linked to other stars such as Cindy Crawford and Sarah Jessica Parker before tying the knot with Carolyn Bessette in 1996. The two remained married until their deaths in 1999.

But despite the split, J. Randy told readers in his 2019 biography The Kennedy Heirs that Madonna and John remained on decent terms, with the late businessman asking Madonna to pose on the cover of his political and cultural magazine George years later. However, she declined.