The students at the University of Manouba, west of Tunis, began the hunger strike Wednesday, Bikyamasr.com reported.
The students are reported to be under medical observation.
The university banned the veils in November over security concerns, and sit-ins by a group of Muslim students protesting the ban had shut down the university for 1 1/2 months.
"I don't wear the niqab or the veil, but I believe that any woman should have the right to dress as she believes is appropriate. That is freedom," university student Hend Mohamed told Bikyamasr.com in an e-mail Thursday.
University officials say they want the protests to end before exams start Jan. 24.
A recent dispute between Islamist and liberal students at Sousse University in Tunisia turned violent, and three students were injured, Bikyamasr.com said.
Uprisings led to the overthrow of former President Ben Ali's regime in January 2011.