The agency will begin working with the client immediately. Mortimer Whittaker O'Sullivan previously handled the business, which it won in 2004. Its most recent work featured Fern Britton.
The process was handled by Carol Welch, the marketing director for Jordans and Ryvita. She said: "We're delighted to be working with Grey. The ideas they presented for taking the Ryvita brand forward were fresh and exciting. Grey managed to build succinctly from our brief and add value to our existing brand equity."