The owner of an espresso bar on the NSW south coast, who chalked a controversial message about Australia Day on a window blackboard has been inundated with death threats since a photo of the sign went viral.

The owner of Mister Jones in Bermagui said his business has been targeted by vandals and his voicemail flooded with threats after a local man photographed the sign "Yes, we're open on national dickhead day" – a reference to them being open for business on Australia Day, January 26 - and uploaded it to Facebook on Monday.

The photo was then shared on the Meanwhile in Australia Facebook page and as of Thursday morning, had been shared more than 3500 times and liked more than 7000 times.