The 50:50 joint retail venture will see an exclusive line of De Beers-branded jewellery sold in an international network of upmarket stores hoping to take on the likes of Tiffany and Cartier.
A flagship London store in Old Bond Street, opening later this year, will be the first site for the £280m venture. Further stores will follow in Paris and New York.
Creative will be led from DDB's Paris agency Louis XIV. Media will be handled by Carat UK as part of a European-wide LVMH agreement.
Louis XIV was awarded the business following the five-year history between the agency and Alain Lorenzo, De Beers LV's chief executive, who was the former chief executive of Givenchy Fragrances and Cosmetics.
Jean-Christophe Gandon, the marketing director of De Beers LV, said: "Louis XIV DDB has had long experience with Givenchy Fragrances, which is part of the LVMH house. There is a relationship and expertise that played a role."
The venture between the diamond giant and LVMH was announced a year ago. The tie-up won regulatory approval from the European Commission to open the exclusive boutique chain in July.
J Walter Thompson handles the global De Beers account, but did not pitch for the joint venture.
Louis XIV was originally launched as a luxury goods arm to DDB Paris, but the two merged last year to become Louis XIV DDB.
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