Ahmed Douma was sentenced on charges of illegal protesting, possession of weapons, assaulting security personnel and attacking government buildings. The Court of Cassation accepted his appeal on Thursday.
The case dates back to December 2011, when clashes broke out between protesters and security forces outside Egypt's Cabinet building. Life sentences were handed down to 230 people in 2015. All but Douma were tried in absentia.
Since the military overthrew an elected Islamist president in 2013, Egypt has jailed thousands of people, including several leading activists behind the 2011 uprising that toppled longtime autocrat Hosni Mubarak.