The female student donned the outfit at an annual school parade to pass out condoms, KDKA-TV, Pittsburgh, reported Monday.
"I think we all know that when we're growing up we do stupid things but to cross over the line in this instance shouldn't happen with anybody," Bishop David Zubik said. "What I do want to have happen is for this person to learn an important lesson."
In response to the diocese's request, the university said it is reviewing the incident and that it will take appropriate action if community standards or laws were violated.
Students at the school said there is no need for punishment, KDKA-TV reported.
"It's all in good fun and it's not meant to harm anyone," Ivy Kristov said.