A woman was followed into the basement of a property and then raped, police said.
The 22-year-old victim was approached by the man in Hanbury Street in Tower Hamlets at about 02:10 GMT on 9 November.
He followed her into a building before the attack and then left around 20 minutes later, the Metropolitan police said.
Detectives have released an image of the suspect.
He is described as a black man, aged between 25 and 35 years old.
He was wearing a dark coloured body warmer which he left behind at the scene of the attack along with a grey hat.
He was then pictured in a grey jumper after the attack.
There have been no arrests.