The order states the tests should be carried out "as soon as possible", to determine if Le Pen "is capable of understanding remarks and answering questions".
Le Pen - who lost to Emmanuel Macron in last year's presidential election - called the move "crazy" in a series of tweets on Thursday.
"I thought I had experienced everything, but no!" For having denounced the horrors of #Daesh in tweets, the "justice" is submitting me to a psychiatric evaluation! "Just how far will they go?" she tweeted. She also posted an image of the court order on her Twitter account with the words: "It's genuinely STAGGERING". The charges stem from Le Pen's decision to post the images, including a photo of decapitated U.S. journalist James Foley, after the Paris terror attacks in November 2015. "This regime is really starting to worry me", suggesting that the case was part of a government plot to discredit her.More news: Tues. 12:40 pm: Trump declassifies some Russia probe papers
Among the list of concerns were whether Le Pen is "in a unsafe state from the standpoint of psychiatry or forensic science".
She has been stripped of her immunity as a parliamentarian and she could still face a fine or even jail.
"A court orders a psychiatric assessment for Marine Le Pen". "I'd like to see how the judge would try and force me do it", she said.
Experts have told the French media that expert psychiatric tests are run of the mill for people charged with these kind of offences and have not specifically been ordered for Le Pen. "She is a political personality but this is not a political decision", Jacky Coulon, national secretary of the magistrates union, reportedly told France Info radio.More news: Here's How Xiaomi Mocked Apple For Steep Pricing Of New iPhones
The images showed the bodies of people who were executed by the Islamic State and included the decapitated body of US reporter James Foley.
The other images showed a tank running over a man in an orange jumpsuit, while another jumpsuit-clad man was shown in a cage being burned alive. She responded by posting a photo of decapitated journalist James Foley, who was killed by Islamists, and wrote, "Daesh is this!"
She later deleted the picture of Foley after a request from his family, saying she had been unaware of his identity, but she has denounced the case against her as a violation of her freedom of expression.More news: True Detective director to make next Bond movie