Since 2006, women have been appointed as advisers only.
The decree comes in response to rights advocates' demands to give a voice to women, many of whom have been challenging the country's religious establishment, which adheres to Wahhabism, one of the strictest interpretations of Shariah law in Islam.
However, the king's decrees reflected how he is treading carefully to not anger powerful religious clerics.
According to the decrees, the female council members must be "committed to Islamic Shariah disciplines without any violations" and be "restrained by the religious veil." The decrees also said that the female council members will be entering the council building from special gates, sit in seats reserved for women and pray in special worshipping places.
Earlier, officials said that a screen will separate genders and an internal communications network will allow men and women to communicate.
The kingdom, which is the birthplace of Islam, enforces strict segregation of the sexes according to its interpretation of Islam. An unrelated couple, for example, can be detained for being alone in the same car or having a cup of coffee in public. Saudis observe such segregation even at home, where they have separate living rooms for male and female guests.