He fled the shop with nothing and was seen by members of the public making his getaway on a bicycle that had been parked outside.
The woman said they had had similar incidents in the past, but had made security moves within their shop to raise the alarm with authorities in the event of an emergency.
"It was so scary. I rang 111 straight away, but I couldn't speak up because I was scared," she said.
Police are appealing for any sightings of the offender, who was seen riding his bike down nearby Olympic Drive before entering the shop.
After leaving the store, he was then seen riding his bike down the same road towards a nearby lake.
He is described as a Maori in his mid-twenties. He was wearing a blue hooded jumper and black pants at the time, as well as covering his face with a black towel.
• Can you help? Anyone with information should contact Whakatane Police on: (07) 308 5255 or CrimeStoppers anonymous on: 0800 555 111.