IRI will supply data, such as shopper and market insights, to all of Nestle UK's division, the first time that one supplier has been handed the business for the whole company.
The contract covers retail data, software and services and runs for three years, with the option of a two-year extension.
Jon Walsh, Nestle UK communication director, said: "Being able to track and respond to consumer needs swiftly and effectively is essential for any business looking to succeed in today's competitive market place.
"Working with one supplier to track consumer, shopper and market brings with it significant efficiencies and cost savings."
Nestle previously used IRI for some of its research needs in Foods & Beverages, Purina PetCare and others.