State news agency MENA said the court in Cairo would announce its verdict on August 10 to allow for "further deliberations".
Mohamed al-Zawahiri was arrested in August 2013 at the height of a campaign of repression of Islamists in the wake of the army's overthrow of the country's Islamist president Mohamed Morsi.
Zawahiri and his co-defendants are accused of having formed "a terrorist group linked to Al-Qaeda" and plotting attacks on government installations, security forces and Egypt's Christian minority, all charges which his lawyer has denied.
Group members allegedly trained at secret camps in districts of Cairo and in the Nile Delta, north of the capital.