The court found the doctor, Mervat Galilah, guilty of "rioting" inside a state hospital where she works and membership in a "terrorist" group, a reference to the Muslim Brotherhood of ousted president Mohamed Morsi.
The now-famous four-fingered Rabaa sign commemorates hundreds of Morsi supporters killed in mid-August when Egyptian security forces violently dispersed their sit-in in Cairo's Rabaa al-Adawiya Square.
"The verdict came as a shock to all of us," the doctor's wife, Essam Ezzat, told Anadolu Agency.
He said the lawyers have already appealed the sentence.
Ezzat denied accusations of his wife's membership in the Brotherhood, which the army-installed interim government has recently designated as a terrorist group.
He insisted that his wife wore the Rabia pin in memory of a fellow doctor killed during the bloody dispersal of the sit-in.