A woman who was indecently assaulted on a Sydney bus was able to take a photograph of her alleged attacker, who police are now trying to track down.

The assault occurred as the 37-year-old woman was travelling on a bus between Burwood and Campsie on November 6, police said.

NSW Police would like to speak to this man about an indecent assault on a Sydney bus. Credit:NSW Police

A NSW Police spokeswoman said the woman boarded the bus about 6.30pm on Burwood Road and, as the bus travelled towards Campsie, a male passenger allegedly repeatedly rubbed himself against her.

Both passengers got off the bus on North Parade at Campsie. The woman told police she took a photograph of the man who assaulted her as he entered a nearby shop.