The incumbent on the business, Proximity London, will continue to work on retaining existing donors.
The agency won the task after chemistry pitches, which were led by the pitch team of Phil Andrews, Steve Aldridge and Kate Waters in 2006.
The news comes just weeks after Wieden & Kennedy was appointed as Save the Children's above-the-line agency. Although the agencies will be in consultation, no joint campaigns are currently planned.
Stephen Andrews, the head of individual giving at Save the Children, said: "Partners Andrews Aldridge has come up with some incisive thinking and innovative approaches that will enable us to take a fresh view of how we approach recruitment in an increasingly difficult and competitive environment for fundraising."
Phil Andrews, the managing partner at Partners Andrews Aldridge, added: "There is a real desire to break the mould in charity fundraising -- a sector which needs to extend its appeal to a whole new range of donors.
"We're going through a thorough piece of strategic work and looking at fresh options."
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