Emily Patterson was enjoying a cuppa when her baby James started crying ahead of his usual sleep time.
After being tutted at by a woman sitting nearby, Emily said she felt obliged to apologise and take James outside.
But as she left, she overheard a group of women accusing her of being neglectful.
Upset and angry, Emily spoke to one of the women.
She said: "I told her I'm sorry they feel my baby's disturbed them and she went to town, saying I shouldn't have let him cry in the pram and was concerned about the patrons being turned away from the noise."
Emily was so distressed by the incident at the Aristrocrat Café in Lane Cove, New South Wales, Australia, she wrote about it on the North Shore Mums Facebook page – and was overwhelmed by the support she received, attracting more than 400 comments.
Emily said: "If I wasn't perhaps as resilient, it could have gone so much worse for me such as if I was a first-time mum and there were a whole lot of other issues.
"My main issue is that the poor old sisterhood had taken a beating that day but after receiving so much support online, I felt the sisterhood made a comeback.
"I know there's a lot in the media about getting breastfeeding to be acceptable in society, but I think the issue is about people judging mothers.
"It's so tragic that people could be so harsh about others."