The agency won the retained brief in a two-way shootout with incumbent agency Porter Novelli, which managed consumer comms projects for the brand for four years.
Blue Rubicon already handles corporate PR for GSK, promoting its brand's nutritional credentials.
The agency said it would aim to 'shift brand associations so that Ribena is not only linked to health and diet, but is seen as a product to enjoy'. Blue Rubicon will also tell Ribena's 'unique supply chain story'.
The move follows GSK's appointment of Unilever communications manager Claire Dixon as director of comms across its consumer and nutritional healthcare business in May.
Dixon took over from Alice Hunt, who has become director of corporate media for the company.