It happened around 1:20 a.m. Saturday near Florence Street and Halstead Avenue.
Authorities said three women were walking home after leaving a local business when a man approached one of them from behind and grabbed her.
Police said the suspect forced the woman to the ground during a struggle and groped her before running off when the victim's friends stepped in to help.
The suspect is described as a man in his early 20s, about 5-foot-10 with a slim build. He was last seen wearing a black hooded sweatshirt, black sweatpants and a black cloth covering his face.
Detectives are reviewing surveillance footage and canvassing the area as they work to identify the suspect.
Police are asking residents and businesses with security or doorbell camera footage from Florence Street, Halstead Avenue and surrounding areas between 1 a.m. and 2 a.m. Saturday to contact investigators.
The investigation remains ongoing.
Anyone with information is asked to contact the Village of Mamaroneck Police Department's Investigations Division at (914) 777-1122. Anonymous tips will be accepted.
Police also reminded residents to stay aware of their surroundings, travel in groups when possible and report suspicious activity immediately.
----------
* More Northern Suburbs news
* Send us a news tip
* Download the abc7NY app for breaking news alerts
* Follow us on YouTube