The 10-strong team, based in Dublin, will build on business generated in Ireland over the past three years by Carla Brooks.
This includes work for Nestle, Colgate Palmolive, Unilever, Procter & Gamble, Masterfoods and Coca-Cola, individually and in collaborative marketing programmes with Tesco.
Brooks will head the new office as commercial director. She is joined by Chris Arnold, head of customer insight, and senior client services director Natalie Harb.
Dublin will be Dunnhumby's third international outpost after London and Cincinnati, which opened in 2003. The aim is to grow staff numbers in Ireland to 30 within the next two years.
Edwina Dunn, Dunnhumby chief executive, said: "The Irish business has built steadily to the point where we need to expand our offices to accommodate the growing demand for our services.
"I have been pleased with the progress we are making in Ireland based on our unique Dunnhumby proposition that helps our clients understand the needs of the Irish consumer in a way that hasn't been possible before."
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