Le Pen, who was an MEP from the 1980s up until earlier this year, was investigated over the improper spending of EU funds after the European Parliament lifted his immunity in March.
Judges questioned Le Pen for more than four hours about the jobs of three of his aides, according to his lawyers.
"The investigating judges ask a lot of questions about a case that I consider a political scam," the 91-year-old Le Pen told AFP.
"It was very long," he added.
Le Pen "is very tired of all this," said lawyer Frederic Joachim, condemning the case as an "incursion of the judiciary into the legislature".
Le Pen had used his parliamentary immunity to prevent anti-corruption investigators from questioning him in June last year about the case.
Le Pen's estranged daughter Marine, who now heads the renamed National Rally, has already been charged in the case.
Investigators suspect the National Front used money from Brussels earmarked for parliamentary assistants there to pay staff for party work in France.
It is alleged that almost seven million euros ($7.7 million) were diverted from the European Parliament between 2009 and 2017.