The Daily Mail alleged Mrs Trump had worked as a part-time escort in New York, and had met her husband, Republican presidential nominee Donald Trump, earlier than was previously reported.
Blogger Webster Tarpley wrote that Mrs Trump feared her past becoming public.
The claims were “outright lying”, lawyer Charles Harder said.
“These defendants made several statements about Mrs Trump that are 100 percent false and tremendously damaging to her personal and professional reputation,” Mr Harder said in a statement.
“Defendants’ actions are so egregious, malicious and harmful to Mrs Trump that her damages are estimated at $150 million dollars,” the statement said.
Mrs Trump, 46, was born in Slovenia and moved to the US to work as a model in the 1990s. She married Mr Trump in 2005.
The article on the Daily Mail website quoted claims published in Slovenian magazineSuzy that Mrs Trump’s modelling agency also functioned as an escort agency, court papers showed.
The newspaper also quoted Slovenian journalist Bojan Pozar, author of an unauthorised biography, who claimed Mrs Trump had posed for nude photos in New York in 1995 and alleged that she had met Mr Trump that year, three years before their reported first meeting in 1998.
Her lawyers said she moved to the US in 1996.
Mr Tarpley meanwhile alleged that Mrs Trump was “reportedly obsessed by fear of salacious revelations by wealthy clients from her time as a high-end escort” and had suffered a “full-blown nervous breakdown”.
Both Mr Tarpley and the Daily Mail have since retracted their articles.