1046 GMT August 20, 2018
The renewed three-month state of emergency will start on Friday, according to the decree.
"The armed forces and the police will take the necessary measures to confront the dangers of terrorism," it said.
Parliament approved the initial state of emergency in April after the two church bombings claimed by the Daesh group that killed at least 45 people.
The state of emergency was then renewed on July 10.
The extremist group said it was behind the bombings in the cities of Tanta and Alexandria, and it threatened further attacks against Egypt's Coptic Christian minority.
Extremists also claimed a Cairo church bombing in December that killed 29 people.
The emergency law expands police powers of arrest, surveillance and seizures and can limit freedom of movement.
Egypt had been ruled for decades under a state of emergency, which was cancelled a month before former president Mohamed Morsi took power in 2012.
Following Morsi's overthrow by Sisi, then an army chief, in 2013, a state of emergency was declared for a month after clashes between police and protesters that killed hundreds and after extremist mobs attacked Christian properties.