The agency picked up the business after a pitch process.
Quiet Storm has most recently worked with Butcher's Pet Care, but split with the brand last year and did not repitch. Butcher's Pet Care spent £1 million on advertising over the past 12 months, according to Nielsen.
The Brooklyn Brothers will work on advertising, digital and consumer PR for the entire Butcher's range of cat, dog and puppy food products.
Andrew Frost, the marketing controller at Butcher's, said: "We have ambitious plans for the brand and we were looking for a progressive agency partner that will integrate all communications tools in support of our marketing effort. We met some great people in the process and are delighted to have found The Brooklyn Brothers."
The media account, held by Walker Media, is unaffected.
Separately, The Brooklyn Brothers has hired Sarah Kavanagh as its head of artistic production. Kavanagh joins from Fallon, where she was the head of art buying.