The customer, Emma, from Melbourne, says after transferring her seedless red grapes into a bowl of water, she discovered what she believed appeared to be a tiny mouse fetus.
Merely the length of the grapes surrounding it, the hairless mouse can be seen lying lifeless on top of the stalk in a photo shared to Woolworths' Facebook page.
"Tuesday night and [I] have well and truly lost my appetite," she explained.
The woman said she was unaware of the "ugly specimen" until moving the grapes to the bowl.
"No further words needed," she added.
Speaking to Yahoo News Australia, she said she was "disgusted" when seeing the mouse.
"I was relieved that I had taken them out to be washed and the mouse didn't go anywhere near my mouth."
She purchased the grapes at the supermarket's Bentleigh store.
Woolworths says find is 'concerning'
Woolworths responded to her post hours later, calling the find "concerning".
Requesting further information on the product, they informed the customer she was entitled to a refund and replacement in store if she was "unsatisfied" with the product.
Emma said she returned the grapes and the mouse to the store where the customer service desk took them off her.
Woolworths informed Yahoo News Australia they have yet to receive any information surrounding the find.
The supermarket says it is an isolated incident.
The discovery comes at a time when NSW, as well as parts of Victoria and Queensland, have been plagued by an influx of mice in recent months.
The rodents have terrorised farmers and caused millions of dollars worth of damage by destroying crops and stored hay and grain.
There is no indication at this stage the discovery is linked to the plague.
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