Weapon-wielding intruders carried out the second attack on a convenience store in the borough in the space of a month.
Three men entered the McColl's shop in Hindley Green carrying kitchen knives and a lump hammer and one of them threatened to attack an employee if he did not open the tills.
The other men then jumped over the counter and stole items from the display, before taking a cash register from one of the shop assistants.
All three men then left the shop with the stolen items and made off in an unknown direction.
This incident, at around 9.30pm on Tuesday October 17, came just a few weeks after the Atherton Road store was raided.
Two men had entered the shop carrying claw hammers at around 9.40pm on Wednesday September 20, threatening staff and asking them to give them money from the till.
When the offenders were told there was no money, they left the store and fled in an unknown direction.
Police believe the two incidents are linked and are appealing for information.
Detective Constable Andrew Partington of GMP’s Wigan borough said: “Both of these incidents must have been terrifying for the shop assistants who were met with these weapons.
“The men posed a serious risk, not only to the staff working tirelessly behind the counter, but to the people who could have been in the shop at the time.
“I’m appealing to anyone who was in the shop, or nearby, when these robberies took place, to please get in touch with us and help with our enquiries.”
Anyone with information is asked to contact police on 0161 856 7225 or 101, quoting crime reference 277631T/17, or ring independent charity Crimestoppers, anonymously, on 0800 555 111.