The smoothie brand, which is majority-owned by Coca-Cola, has been contacting agencies to pitch for the brief. An appointment is expected by the end of June.
The incumbent, 101, is not taking part in the process, which is being handled by Agency Insight.
101 has worked with Innocent since 2013, when it won a competitive pitch.
The agency’s work for the brand included the "tastes good, does good" campaign.
Before 101, Innocent had a reputation in the industry as a promiscuous client, reviewing its creative account six times in six years and working with shops including Fallon and Rainey Kelly Campbell Roalfe/Y&R.
Laurence Green, a partner and co-founder of 101, said: "We’ve worked with Innocent for over three years on a project basis. We’re proud of the work we’ve produced.
"For now, Innocent turn their focus towards mainland Europe. But who knows what the future holds, and I hope our paths cross again."
Tim Clarke, Innocent's group marketing and innovation director, said: "These are exciting times. Our brand is in growth throughout Europe, and we are within touching distance of becoming Europe’s favourite little juice company. Our new agency partners will help us to accelerate this rapid growth and to write the next chapter of the innocent story."