Fahima will also be subjected to a year-and-a-half period of probation.
As part of the deal, Fahima has confessed to offenses of contact with a foreign agent while intentionally trying to undermine national security, providing the enemy with information, and violating a legal order.
Fahima is to be released from prison in another 10-and-a-half months.
The State Prosecutor’s Office together with Fahima's attorneys announced the plea bargain on November 30.
Under the agreement, three clauses were removed from the original indictment, including aiding the enemy at a time of war, possession of weapons and supporting a terror organization.
The judges wrote in their verdict Thursday that they "could not lessen the magnified severity of the offenses the accused has been convicted of even after the indictment was amended - in regard to punishment that follows these crimes, including 15 years for each offense related to national security and two years for violating a legal order – as well as nationally, socially and morally."
"Thus, we view with great importance the confessions made by the accused to these offenses, especially her positive remarks in court, showing a change in attitude in comparison to her comments during the investigation, her attitude towards defense officials and during court deliberations."
The judges added that the plea bargain is balanced, appropriate and compatible with the judicial policies of the court and therefore they decided to approve the deal.
Fahima supporters express disappointment
The Fahima affair has been going on for several years. It started when the young Israeli woman befriended Fatah members in Jenin, headed by wanted terrorist Zakaria Zubeidi.
Following her trips to Jenin during the Intifada, Fahima was arrested and charged with aiding Fatah members act against the IDF. She claimed her relations with the group were friendly and humanitarian only.
Members of a committee established to promote Fahima's release expressed their disappointment after hearing about the plea bargain.
Committee member Yael Lerer said that "this is a kind of political persecution.“
"I think Tali will continue to act against the occupation, she is very determined to do so. I believe that she will do so without violating the law, especially now that there is a period of probation for those offenses as part of the plea bargain," she added.