The agency fought off competition from DDB, Clemenger BBDO, Saatchi & Saatchi and Whybin\TBWA after the incumbent M&C Saatchi resigned the account following its Tourism Australia win.
The new team will take over the account immediately with the aim of expanding New Zealand's international profile. It will build on the "100% Pure New Zealand" campaign developed by M&C Saatchi.
Tourism New Zealand chief executive George Hickton said JWT/Assignment will provide the tourism body with the combination of an extensive worldwide network and an internationally acclaimed New Zealand campaign.
Mike Connaghan, JWT managing director Australia and New Zealand, said: "Tourism New Zealand is arguably the most prestigious account in New Zealand.
"The win is incredibly important for us in New Zealand. We have been rebuilding for the last year, so securing Tourism New Zealand at this stage is wonderful."
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