The agency, which already works on the ad account for Rimmel, will now handle the brand's global digital strategy and online requirements, including a revamp of its website later this year.
Previously, Coty worked with agencies on a market-by-market basis, but the company decided to align its global digital activity into one agency.
The appointment was made as part of an ongoing review of Coty's digital roster. The pitch was called in March.
JWT's digital campaigns for Rimmel, which is the largest cosmetics brand in the UK, will be integrated with above-the-line activity.
The agency has handled Rimmel's global advertising since 1997, but was forced to repitch for the business last year, successfully retaining the account after a review that also involved Fallon London and Laird & Partners New York.