Le Pen was in March handed a five-year ban from holding public office, effective immediately, after she and eight other former National Rally (RN) lawmakers were found guilty of misusing over four million euros ($A7 million) of EU funds.
Judges said that between 2004 and 2016, Le Pen and others had used funds earmarked for work at the European Parliament to pay staff who were actually working for the party.
The party itself and a dozen parliamentary assistants were found guilty of receiving the money.
In the few words Le Pen said in court on Tuesday, she struck quite a different tone from her first trial, in which she had staunchly denied doing anything wrong and had accused judges of being politically biased.
Instead, on Tuesday, she said that if she potentially did something wrong, it was unintentional.
"I wish to state at the outset that, if any offence was committed, I want the court to understand that we had absolutely no sense of doing anything wrong whatsoever," Le Pen said.
"The European Parliament did not warn us of anything, as it could have done," she said, adding: "I firmly believe we never concealed anything."
Le Pen also initially received a four-year prison sentence - two years of which were suspended and two years to be served under home detention, and a 100,000 euro ($A174,354) fine. Unlike the ban, those penalties did not take effect because she appealed.
The RN and 10 others found guilty of diverting European Parliament funds or receiving these funds have also appealed.
The hearing is due to end on February 12. Le Pen will be interrogated by the court at length next Tuesday and Wednesday.
The European Parliament's lawyer Patrick Maisonneuve said he hoped Le Pen and her co-defendants' convictions would be upheld, including more than three million euros ($A5.2 million) awarded in damages to the European Parliament.
The RN was also ordered to pay a two million euro ($A3.5 million) fine, with half the amount suspended.
A ruling is expected before the summer, meaning Le Pen's hopes of running in 2027 remain alive if her five-year ban is revoked or drastically curtailed.
If she cannot run, her protege, 30-year-old RN party president Jordan Bardella, is expected to step in.
