Trimedia director Frankie Oliver said the campaign, which will run from April to August, will be ‘humorous’ and accompanied by advertising by Mother.
PR will target lifestyle and food media as well as radio and weekend newspaper supplements.
Trimedia, which provides PR support for Diageo’s Gordon’s Gin brand, saw off two other agencies to secure the business on fees of more than £100,000.
Pimm’s last two summer campaigns were managed by Borkowski PR.
The drink itself was created in 1820.