Firefighters were called to the shop, on Ruam Pattana Rd in Moo 3, Ratsada, at about 7:40pm.
Soon to arrive at the scene were Phuket Governor Narong Woonciew, Phuket Provincial Administrative Organisation (PPAO) Vice President Tiwat Sidokbub and Maj Panukorn Wankaew of Phuket City Police Station.
Five fire trucks arrived to counter the blaze, which is believed to have started by a short circuit at the store. Power supply to the building was cut before firefighters attempted to douse the flames.
When officers arrived, they found the flames burning strongly and a large cloud of smoke billowing out of the building.
The fire was concentrated in a storage room where a lot of cardboard was kept at the back of the shop.
Joined to the back of the building was a single-storey wooden house where the shop owner lived.
Firefighters took about one hour to bring the fire under control, and managed to prevent the fire from spreading to any adjacent buildings, including the home and the two shop units joined to either side of the store.
The back of the grocery store was heavily damaged by the fire. The front of the shop suffered water damage.
An estimate of the damage caused by the fire has yet to be determined.
Werayut Mannui was in the home with two friends when he heard what sounded like electrical wires combusting. Then sparks were seen falling into the storage room, which quickly caught fire.
He and his friends were unable to put the fire out, hence they called the fire department, he said.
His sister had the house built and he came to look after the shop in August last year, Mr Werayut added.
Police have yet to confirm the cause of the fire, which officers said was still under investigation.