The first lady applauded the 25-year-old model on Twitter after Ratajkowski called out a New York Times reporter who told her Trump is a "hooker."
"Applause to all women around the world who speak up, stand up and support other women @emrata #PowerOfEveryWoman #PowerOfTheFirstLady," she tweeted.
Ratajkowski had told her 983,000 followers that she had spoken to the reporter in question during an event Sunday evening.
"Sat next to a journalist from the NYT last night who told me 'Melania is a hooker.' Whatever your politics it's crucial to call this out for what it is: slut shaming. I don't care about her nudes or sexual history and no one should," she wrote.
"Gender specific attacks are disgusting sexist bull[expletive]," the star added.
The New York Times acknowledged the incident in a statement the same day, describing the reporter's remark as "inappropriate."
"At a party last night, a Times reporter who does not cover Washington or politics referred to an unfounded rumor regarding Melania Trump," the publication said.
"The comment was not intended to be public, but it was nonetheless completely inappropriate and should not have occurred. Editors have talked to the reporter in question about the lapse," the company added.
Ratajkowski had said in December that she stands for "women choosing when and how they want to share their sexuality and bodies." She previously wrote in an essay for Glamour that it's "society's responsibility to change the way" it views women.