The appointment fills the gap left by Partners Andrews Aldridge, which resigned the business in April last year over strategic differences.
AIS will develop the strategic and creative direction for the charity's fundraising activity, following a six-month consultancy period.
AIS will work closely with Bartle Bogle Hegarty to develop a strategy that complements the charity's advertising. Activity will target existing donors. AIS will also trial a strategy targeting prospective donors in the autumn.
Diana Green, the director of communications at Barnardo's, said: "Our fundraising challenge is to leverage growth from a strengthened brand platform and a more integrated approach. AIS has been brought in to challenge strategic thinking and deliver results. We have never had a strategic relationship across our DM and below-the-line activity and have high hopes for the benefits that appointing a lead agency will confer."
Stuart Archibald, the AIS managing partner, added: "This is a hugely exciting opportunity to get to work with the iconic Barnardo's brand on an extremely important cause."
Last November, Barnardo's appointed Rapier to handle the direct marketing assignment for its annual Big Toddle fundraising event for the next five years (Campaign, 4 November). This relationship will not be affected by AIS's appointment.
The charity's advertising through Bartle Bogle Hegarty has included the controversial "silver spoon" campaign, which featured images of babies with a syringe, a cockroach and a bottle of methylated spirits in their mouths.
Barnardo's works with approximately 120,000 children, young people and their families across more than 371 projects in local communities across the UK.