The victim, a 33-year-old woman, was walking through the Tamarisk Road estate in South Ockendon at around 7.25am on Friday August 5 when the incident happened.
The woman was followed and when she reached a walkway between Larkspur and Tamarisk Road the man grabbed her and sexually assaulted her. The victim screamed and the man ran away.
The suspect is described as a white man, aged in his mid 20s, around 5ft 10ins tall, slim with a slim face and “pointy nose . He wore a navy blue tracksuit with the hood up.
Witnesses can contact investigating officer PC Emma Ridings at Grays police on 101 or Crimestoppers anonymously on 0800 555 111.