Pearce will head the agency's planning activity, under the banner Soulsearch, which integrates consumers' media behaviour into the agency's planning process from its initial stages.
She will report to Soul's strategic partner, Kevin Brown, and will work alongside the recently appointed Mark Swift, who heads Soul's media offering, Soul Space. She will work across all of the agency's accounts.
Pearce started her career on the client side, working as a brand manager on Olivio at Unilever. She then took on a number of planning roles at agencies including McCann-Erickson, Leo Burnett and TBWA/London. In 2001, she set up Blazye Pearce with Chris Blazye, a founder of Malcolm Moore Deakin Blazye.
Brown said: "Jo brings a breadth of client and agency planning experience, and understands our culture and way of working."
Pearce added: "Soulsearch is an integral part of the Soul offering. It forms the anchor to everything we do, and is designed to get ourselves and our clients to a definitive brand idea and an informed, focused brief."