The review is being handled by the AAR, with the incumbent Tangible Response repitching for the business.
The successful agency will work on a communications strategy and creative executions aimed at both raising the charity’s profile and increasing its income.
Over the last four years Tangible Response has primarily carried out direct marketing activity.
An agency is expected to be appointed by mid September.
World Horse Welfare was previously known as the International League for the Protection of Horses. It underwent a rebrand last year with a fresh identity in a bid to broaden its appeal and attract new supporters.
The new identity was created by StrategicFusion.
Roly Owers, World Horse Welfare chief executive, says: “Following our re-branding in 2008, we’re ready to build on our excellent operational reputation, with profile raising amongst both existing and new target audiences, to ultimately engage and inspire horse lovers.”