The agency was appointed on the spot after presenting an idea based on the classic British film 'The Italian Job'.
It takes over the work following the collapse of Faulds in September, which also held the media planning and buying for the work until July this year, when it lost the business to MediaCom.
JWT has been charged with developing the "Find your perfect partner with Auto Trader" campaign created by Faulds, which highlights the love match between car-loving Auto Trader and its car-loving readers.
Auto Trader, which publishes 13 regional magazines for people buying and selling cars, as well as running the UK's biggest motoring website, is owned by Guardian Media Group. GMG paid £572m to buy the 52% stake of Auto Trader that it did not already own from the venture capitalists BC Partners.
Matt Thompson, marketing director at Auto Trader, said: "JWT has taken a powerful advertising property and has demonstrated that it can develop a successful platform and vision for the next stage and direction of our campaign. In JWT, I think we have found our perfect partner."
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