She was pictured drinking coffee in a cafe but declined to answer when asked if she was meeting President-elect Donald Trump.
Ms Le Pen is currently one of the top two candidates for the first round of voting in April, opinion polls suggest.
The National Front leader has called Mr Trump’s election “an additional stone in the building of a new world”.
Sean Spicer, who will be Mr Trump’s press secretary, re-tweeted a post by CNN’s Noah Gray that Ms Le Pen would not be meeting Mr Trump or anyone from the transition team, adding “Trump Tower is open to the Public”.
Trump team spokesperson Hope Hicks also said Ms Le Pen was “not meeting with anyone from our team”, Politico reported.
Ms Le Pen was seen with three men in the cafe. Agence France-Presse identified one as her partner, Louis Aliot, the National Front’s (FN) vice-president.
Media captionLe Pen praises the Trump victory, speaking to the BBC’s Andrew Marr
Ms Le Pen also declined to answer when asked whether her visit was personal or professional.
But when asked if she would speak to pool journalists later, one of her associates said “OK”.
Her campaign manager had earlier said she would not be meeting Mr Trump on her visit to New York.
Ms Le Pen has herself referred to her trip as “private”.
Marine Le Pen is the daughter of ex-FN leader Jean-Marie Le Pen, a convicted racist. She has denounced her father’s comments and has sought to distance herself from such toxic issues as Holocaust denial.
She retains a hard line on immigration and has linked it to militant Islamism.
Ms Le Pen opposes the European Union, open borders and globalisation.
She also says jobs, welfare, housing, schools, or any area of public provision should go to French nationals before they go to “foreigners”.
She is likely to fight former Prime Minister Francois Fillon and Socialist Prime Minister Manuel Valls for victory in the first round of voting in the presidential election. It is then expected to go to a run-off.