The ice cream, called Baby Gaga, is made with milk expressed by 15 women who replied to an advertisement posted on an online mothers' forum.
Each serving of Baby Gaga at the Icecreamists cafe in trendy Covent Garden costs £14 ($22.5, 16 euros).
One of the milk donors, Victoria Hiley, 35, said that if adults realised how tasty breast milk was then more new mothers would feel happier about breastfeeding.
She expressed the milk at the cafe and it was pasteurised before lemon zest and vanilla pods were added during the churning process.
Hiley, who is paid £15 for every 10 ounces of milk she donates to the company, told the BBC: "What's the harm in using my assets for a bit of extra cash?"
The founder of Icecreamists, Matt O'Connor, said he could not understand people being squeamish about the product.
"If it's good enough for our children, it's good enough for the rest of us," he said.
"Some people will hear about it and go yuck -- but actually it's pure organic, free-range and totally natural."
A spokeswoman for Icecreamists said that despite the success of Baby Gaga there were currently no plans to market the breast milk ice cream more widely.
"This was launched this week and already the ice cream has sold out," she told