The agency, which won the brief without a competitive pitch, will be responsible for creating ways of connecting J&B with its core 18- to 24- year-old market.
M&B's work will initially focus on ideas for the Spanish market, then Mexico. The brief is to create ideas beyond traditional advertising that will bring the brand to life.
M&B secured a similar international role for Unilever this summer, briefed to develop communications channels with consumers outside traditional advertising.
J&B is the number-two Scotch in the world and number one in Europe, but it is trying to appeal to young drinkers against stiff competition from white spirits and ready-mixed drinks.
Iain Kennedy, J&B's global brand director, said: "With its work for other brands, M&B has proven it can deliver powerful ways of connecting brands with their consumers. This is precisely the kind of brand engagement that J&B needs right now."
Paul O'Neill, a partner at M&B, added: "The brand is one of the most famous. The brief is challenging. And this client is hungry for new ideas."
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