The court found against Marzouki on charges of "assaulting the external security of the state", according to the state news agency TAP.
Marzouki, who lives in Paris, has described Saied's seizure of powers in July as a coup, called for protests against him and urged that a major international meeting of French-speaking countries be moved from Tunisia.
Saied has rejected accusations that his seizure of powers, suspension of parliament and plans to change the constitution are a coup. He said he acted to end protracted political paralysis and that a referendum will be held next year on a new constitution followed by parliamentary elections.
Foreign donors needed to help address a looming crisis in Tunisia's public finances have urged Saied to restore normal constitutional order and say democracy and freedom of speech are important to their relationship with the North African country.
After Tunisia's 2011 revolution that introduced democracy, an elected assembly appointed Marzouki as the interim president, overseeing the transition to a new constitution in 2014.
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