The private Bandeirante University in Sao Bernardo do Campo, outside Sao Paulo, said 20-year-old Geisy Arruda disrespected "ethical principles, academic dignity and morality."
Bandeirante University published newspaper advertisements Sunday accusing Arruda of attending class with "inadequate clothing" and having a provocative attitude that was "incompatible with the university environment."
Arruda made headlines after the Oct. 22 incident, in which she had to be escorted away by police after wearing the mini-dress to class. She put on a professor's white coat and left amid a hail of insults and curses.
In the ad, titled "Educational Responsibility," the college said it had warned Arruda to change her behavior and decided to expel her after talking to students, staff and Arruda herself. It accused her of posing for pictures and provoking other students.
The university said it was also temporarily suspending some of the students who were seen heckling Arruda in a video of the incident that made the rounds on Youtube. It did not say how many were being suspended or how long they would be kept from attending classes.
Brazil's national student union released a statement on Sunday saying it was against the university's decision to expel Arruda, and Brazil's top official for women's policy, Nilcea Freire, told the official Agencia Brasil news service that the decision showed "intolerance and discrimination."
Although Brazil is known for its skimpy attire, especially in beach cities, most college students dress more modestly on campus - commonly in jeans and T-shirts. Some students had complained that Arruda seemed out of place in her revealing clothes, Brazilian media reported.