Officers believe the woman could hold vital information about the incident in which a conductor was grabbed by her hair and pulled off a tram near to Cricket Inn Crescent, Wybourn.
A South Yorkshire Police spokesman said: “At about 3.30pm on Tuesday, December 8, it is reported that a woman, believed to be in her early 20s, assaulted a female tram conductor on the Meadowhall bound Sheffield Supertram, near to Cricket Inn Crescent.
“The offender reportedly grabbed the conductor by her hair before pulling her off the tram.
“Were you on the tram at the time of the incident? Did you see what happened?”
Anyone with information should call South Yorkshire Police on 101 or Crimestoppers on 0800 555111.