The disturbance happened around 9.15pm at the Best One store on Prestonpans High Street, East Lothian.
A man entered the premises and began shouting racial abuse at staff whilst acting aggressively.
A male customer then escorted the man from the shop and police were contacted.
Officers are now keen to hear from anyone who can assist with their enquiries.
The suspect is described as white, around 30-years-old, 5ft 9ins tall with a medium build and short light-brown hair. He was wearing white trainers and a grey Jack Wills hooded top with “Wills” on the back and JW on the front.
A police spokesman said: “The suspect did not physically assault any of the staff or customers within. However, his demeanour was of concern to them and we are carrying out enquiries to establish his identity.
“We are particularly keen to hear from the customer who removed the man from the store and would ask him to contact police immediately.
“Similarly, anyone with any other information that can help our investigation is also asked to come forward.”
Anyone with any information can contact Lothian and Borders Police on 0131 311 3131, or the charity Crimestoppers in confidence and complete anonymity on 0800 555 111.