Mandurah detectives are investigating an incident which occurred on Sholl Street near Pinjarra Road in Mandurah on Monday, August 7.
About 9:35pm a male on a bicycle approached a 20-year-old female near the church.
The male engaged the victim in conversation before grabbing her arm, forcing her to the ground and indecently assaulting her. The victim was able to break free and the male made off towards Gibson Street with his bicycle.
The man is described as about 20 years old, fair skinned but tanned, approximately 180cm tall, brown hair and unshaven. He was wearing a black jacket with a grey hood and black pants. The male was had a dark coloured bicycle.
Detectives would like to speak to anyone who was in the area on Scholl Street on Monday, August 7 between 9:20pm and 10:00pm.
Detectives would also like to speak to anyone who travelled along Scholl Street at the same time in a motor vehicle that may have dash-cam footage.
Anyone with information can contact Crime Stoppers on 1800 333 000 or report online at crimestopperswa.com.au.