An anti-vaxxer's unprovoked attack on a Sydney café over its COVID-safe signage has spectacularly backfired and instead saw the business flooded with support.

In a video shared online, a man filmed himself yelling at a barista at the Cafe Dzajko in Tempe yesterday afternoon.

The café was displaying the same NSW Government signage seen in stores across the state which asks customers to check-in and show their proof of vaccination.

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"What make you think that I am going to hand over my medical and private information of whether I am vaccinated or not vaccinated just to buy a cup of coffee," the man in the video can be heard saying.

He then accused the café of "discrimination and putrid attempt to segregate".

Barista Andressa Kist kept her cool despite being terrified as she made coffee yesterday afternoon.

"I am a little bit scared and frustrated because I was just following the rules," she told 9News.

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Owner Diche Dzajko described the man as "faceless" and accused him of "going around attacking people for no reason".

However, the attempt to shame the café backfired with people across Sydney and beyond pledging their support.

Mr Dzajko said people had been giving them extra money with their coffees, and even writing on their Facebook page.

"Best wishes from Canberra. Will grab a brew when I visit next," one person wrote.

"I'm going out of my way to get coffee from you next time I'm in Sydney," another said.