The company has shortlisted The Big Kick, Billington Cartmell, Chemistry and Saatchi X to compete for the business.
Agencies have been briefed to come up with a strategy that involves TV, press and experiential to promote its entire range.
Ella's Kitchen is fourth in the organic baby-food market, behind Hipp, Organix and Plum Baby.
The appointment of an agency will mark a change in the company's communications strategy. It has previously worked with Viacom Brand Solutions, which has run ads on its channels.
Its first activity was a TV campaign that ran on Nickelodeon, NickToons, Nick Jr and Nick Jr 2 and was developed by the Advertising Marketing Partnerships division of VBS and the children's specialist Prism Entertainment.
A spokeswoman for the company confirmed it was looking to appoint an agency but said it would continue to work with VBS.