Cyphus Mason joins from CMW where she worked for five years as account director on Porsche GB, Marbles and The John Lewis and Waitrose Partnership Card.
Spinnaker won the baby food account in January.
In another hiring for the agency Adrian Stainforth joins as a senior developer.
Stainforth will work alongside Spinnaker's growing digital team as a front end developer across most of the agency's accounts.
He has previously worked at Agency.com, Aquent, Tidal Wave and most recently, at Australian digital agency Lavender.
Robert Goldsmith, managing partner at Spinnaker, said: "Both Jo and Adrian bring with them talent and years of experience.
"We're delighted to have them on board and we're sure that our clients will benefit from their enthusiasm and input in the coming months."