The incident happened by an entrance of the shopping centre at 7.30pm on Friday (February 21).
Officers were called to the scene and found a member of staff with minor injuries.
A 21-year-old man was arrested on suspicion of actual bodily harm, but he has been released on police bail as the investigation continues.
Crowds of people were at the scene watching over the fight, with some yelling “stop it” as the staff laid on the ground.
Westfield has been approached for comment.
A Met Police spokesperson said: “Around 7.30pm on Friday, 21 February, police attended Westfield Stratford City, following reports that a man had assaulted staff at a shop. One staff member suffered minor injuries.
“A 21-year-old man was arrested at the scene on suspicion of actual bodily harm. He has been released on police bail pending investigation.”
