The agency was handed the business without a pitch by Fresh Retail Ventures, the licensee for the Jamie Oliver brand. Work is scheduled to start this month.
Saatchis' first brief is to launch Oliver's range of six new pesto sauces. The work will run across print and online media.
Earlier this year, FRV relaunched the Jamie Oliver food and non-food ranges in Tesco and Waitrose, appointing Design Bridge to create the designing and packaging.
Jane Hilton, the head of marketing at FRV, said: "We're increasing our investment in marketing, and Saatchis is the ideal partner for us as we grow the Jamie Oliver food range and its appeal."
Paul Silburn, a creative partner at Saatchis, added: "This is a great win for us. Although Jamie's brand is well established, the food range is still in its infancy, so there's a real opportunity for us to work with Jane and her team to help grow the brand."