"Our research shows that when a bystander steps in, the behaviour shuts down very quickly," said Sex Discrimination Commissioner Elizabeth Broderick.
Work sexual harassment goes largely unreported, with only 20 per cent of victims speaking up.
And more often it is the victim who will leave the company as a result.
Ms Willis said sexual harassment puts a victim in a difficult situation.
"We recognise if you make a report you still have to go into the workplace with that offender," Ms Willis said.
New South Wales Detective Chief Superintendent John Karlatec encourages victims to report it.
"First and foremost, the victim is not to blame," he said on Thursday.
- AAP