The incident occurred about midday as the tram was pulling up to a stop on Eastern Road, near Kings Way. The driver heard passengers yelling and immediately opened the doors, according to Rail, Tram and Bus Union Tram and Bus Division secretary Tarik Koc.
A man allegedly fled the tram and was chased by two passengers before police arrived and arrested a 37-year-old man with no fixed address.
The woman was treated at the scene and then taken to hospital. Koc said the tram driver had been advised to take trauma leave.
“People need to have confidence on board public transport,” he said, calling for greater protections for both passengers and public transport workers.
Nearby volunteers Liz Oxenbury and Liz Redfern, who were working at a charity, said they heard sirens and saw police cars arrive. “Then all the police came along with lots of cars,” they said. “We looked out of our office and there was someone being put into an ambulance. You go on the trams thinking you’re going to be safe, not going to be attacked.”