At around 10.45pm on July 12, a woman was travelling on a southbound Victoria line service from Finsbury Park to Kings Cross when a man allegedly upskirted her.
The woman left the train at Kings Cross station, where the man followed closely before running off.
Officers believe the man pictured may have information that could assist their investigation.
Anyone with information can contact British Transport Police by texting 61016 or calling 0800 40 50 40, quoting reference 881 of 12 July.
Alternatively, Crimestoppers can be contacted anonymously on 0800 555 111.