The Australian restaurant, part of the Seagrass Boutique Hospitality Group, has opened its first branch in Teddington, south-west London.
The agency is tasked with handling all trade, consumer and digital PR around the launch to ensure its success.
Frank Australia is already the agency of record for Seagrass in Australia.
The restaurant group regards the UK as one of its largest potential growth areas, along with the US and South Africa.
George Stathakopoulos, managing director at Ribs & Burgers UK, said: "We are a fast-growing global brand, expanding into new countries, and need an agency to drive the first UK launch and establish our brand in a new market."
Andrew Bloch, founder and group MD of Frank PR, added: "To be part of the UK launch of an internationally renowned brand with a fantastic reputation is an exciting challenge. We are looking forward to adding some creative Frank thinking and ensuring a successful launch."