The dropped charges included illegal assembly, breaking a government-imposed curfew, disturbing the peace, and inciting violence.
In August, security forces cleared protest camps at Rabaa Al-Adaweya and Nahda Square, where demonstrators were protesting against the removal of President and Muslim Brotherhood member Mohamed Morsi.
The Muslim Brotherhood, tolerated under deposed President Hosni Mubarak, rose to prominence during the Egyptian Revolution in 2011. Muslim Brotherhood member Mohamed Morsi was elected president in 2012 and removed from power by the military in July 2013. Since then, tensions have spiked between security forces and Muslim Brotherhood supporters.
The U.S. and United Nations have criticized the Egyptian judicial system for imposing mass sentences against Muslim Brotherhood members and supporters. It is unclear what prompted Monday's acquittal.