A police spokesperson said three people with weapons allegedly entered Night 'n Day Papanui on Main North Rd about 10.40pm on Monday.
They demanded the shop worker hand over any cash and fled the scene.
The three suspects made a quick exit and were gone by the time police arrived shortly after the incident.
The spokesperson said a scene examination has been completed. Police are now working to identify the offenders.
A resident told chrislynchmedia.com there was a large police presence in the area after the robbery.
The resident saw police photographers outside the store on Tuesday morning.