Khalida Jarrar, a senior member of the leftist Popular Front for the Liberation of Palestine (PFLP) and a well-known political figure, was sentenced on Sunday at the Ofer military court near the city of Ramallah in the occupied West Bank.
She had been arrested in April on a series of charges, including encouraging attacks against Israel and violating a travel ban.
"Jarrar was sentenced to 15 months on the charges she was arrested for a few months ago, including incitement of terrorism," an army spokesperson told AFP on Monday.
The Palestinian prisoner rights group Addameer said she had also been fined 10,000 shekels ($2600, 2400 euros) and given a five-year suspended sentence.
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Israel considers the PFLP a terrorist organisation and at the time of her arrest the Israeli army said she posed unspecified "substantial security risks".
Issa Qaraqe, Palestinian minister for prisoner affairs, condemned the trial, calling it "arbitrary and legally unjustified."
"This is a political arrest. The charges against her are fabricated and ridiculous... There are no security reasons as claimed by the Israeli authorities," he told AFP.
In August 2014 she was ordered to leave Ramallah within 24 hours and to move to Jericho, but announced at the time she would disobey it.