It occurred at around 9pm on Thursday 21 August 2014, in the Friargate area.
The victim, a 19-year-old woman, had just left Yates Wine Lodge and was heading towards the old fire station when she was approached from behind and sexually assaulted in an alleyway off Friargate.
The suspects are both described as Asian and aged in their mid-twenties. One of them had spiky hair and a very thin build. The second man is described as having a chubby build.
Detective Sergeant Matt Dodson, of York CID, said: If you were in the Friargate area around the time of the incident and noticed anyone acting suspiciously, I urge to contact the police immediately as you may have vital information which could help this enquiry.
Anyone who can assist the investigation should contact York CID on 101, select option 2 and ask for the department by name. Alternatively, information can be emailed to firstname.lastname@example.org
For those who would prefer to remain anonymous, please contact Crimestoppers on 0800 555111.
Please quote reference number 12140142651 when passing on information about this incident.