The pitch process was handled by marketing services agency Oystercatchers. The Romans and Social Chain were among the agencies involved.
Porter Novelli will begin work on the six-figure brief next week, initially handling consumer PR and social media for a series of new product launches.
The agency will also work alongside ad agency Droga5, media firm Total Media and marketing consultancy TransgressiveX to deliver an integrated campaign designed to expand Rustlers' fan base.
The appointment follows Kepak's recent decision to retain Porter Novelli as its corporate affairs agency in Dublin and take on the services of the agency's brand reputation management team in London.
Brand comms director Clare Hindley, who will lead the account, said: "Kepak have managed - within a relatively short period of time - to create a fan-base of loyal burger lovers who are hungry for relevant ways to engage with the brand. We can't wait to start work with the Rustlers team to develop integrated campaigns that maximise impact and enhance perception of the brand in the UK."