The woman, who is aged in her 20s, was walking up Mont Cochon at about 11 pm when two men passed her.
One grabbed her wrist before she managed to run off, according to the States police.
The man who grabbed the woman is described as chubby, aged in his late 30s, of Mediterranean appearance and about 5-ft 8-ins tall.
He had a receding hairline and was wearing jeans and a burgundy or deep red hooded top. He was heard to be speaking in a foreign language, either Portuguese or Spanish.
The second man is also described as having a Mediterranean complexion. He is 6-ft tall, of skinny build and aged in his early 30s. He was wearing a dark suit jacket with a light shirt underneath.
Anyone with information is being asked to phone the States police on 612612 or Crimestoppers on 0800 555 111.
