FCB Inferno has won Battersea Dogs & Cats Home's creative business after a three-way pitch with VCCP and Wieden & Kennedy.
The agency will aim to bring to life the charity's new organisational strategy based on the theme of "reframing rescue".
An ad campaign, planned for launch in September and running through 2020, will focus on trends in ethical sourcing.
Sarah Matthews, director of marketing and commercial at Battersea Dogs & Cats Home, said: "We are thrilled to be working with FCB Inferno to engage more people with rescue animals and make the greatest possible difference for dogs and cats everywhere."
The charity has previously worked with Karmarama and, before that, it used a umber of agencies on an ad-hoc basis.
Sharon Jiggins, executive vice-president at FCB Inferno, added: "Agencies dream of working on a brand like Battersea. It’s such an iconic and inspiring charity that continues to drive sector-leading change in the welfare of dogs and cats."