The warning was issued by Dar al-Ifta, Egypt's state-sponsored body that issues rulings on Islamic Sharia law.
The warning came after the Islamic State posted calls on social media for marriages via video conference.
Dar al-Ifta said that adhering to such calls "goes against Sharia" and pushes women into "the circle of extremism and terrorism through illegitimate marriages that neither please Allah nor his Prophet."
According to a report by the London-based Institute for Strategic Dialogue, woman seeking to join the Islamic State in Iraq and Syria may finally marry the militants, keep their houses and bear their children.
Meanwhile, Egyptian authorities have imposed restrictions on male citizens between the ages of 18 and 40 travelling to Turkey and Libya.
The goal is to prevent them from joining the Islamic State, which has captured large areas in Iraq and Syria and also has a presence in Libya.
