The determined mothers braved the freezing weather and fed their children in front of Christmas shoppers in Brighton, East Sussex.
The protest was organised by Claire Jones-Hughes, 38, after being confronted by customers in a cafe for breastfeeding her four-month old daughter, Callie, last week.
"One woman said, 'It was very unpleasant watching you feed. You should have covered up more," she told the BBC.
You usually get nice comments when you're with a baby. In their world, it was completely unnatural that they should see me doing that.
Mrs Jones-Hughes was so shocked by the reaction she drummed up support online to stage the flashmob protest.
"I've had comments from all over the country about how great it is to make a stand," she said.
"I've got two daughters who may have children themselves one day. If they choose to breastfeed in the future I'd never want anyone to make them feel how I felt."
The own of the Wai Kika Moo Kau café, Farak Bulut, said he supported the right of mothers to breastfeed their children where they want.
"The restaurant was very busy when the incident happened so I wasn't aware of it until afterwards.
"We support the idea that mothers should feel free to feed their babies and we never make it difficult for them. In fact, the cafe is very popular with mothers."