Wednesday's protest saw women gather in central Tunis to chant: "Our dignity is in the preservation of our rights."
Demonstrating journalist Ilham Barrouta said: "The Tunisian woman is present in every sphere of public life and was at the forefront of the revolution."
Tunisia's personal status code gives men and women equal rights relating to divorce and bars polygamy, but many fear that the assembly elected to write the country's new constitution may reverse these protections.
Islamist groups did well in the elections and some wish to impose sharia law, under which men can marry up to four women. Students associated with the ultra-conservative Salafist movement have attacked woman teachers at universities in recent weeks.
The National Transitional Council in neighbouring Libya has already announced its intention to impose sharia law on the country.