Mindshare won the account after a four-way pitch that included the incumbent, Omnicom-owned M2M, MPG and Starcom MediaVest Group.
M2M has held the business since 2006, when it took the account from Vizeum in a pitch that also included Mindshare and Starcom MediaVest Group.
Mindshare will be responsible for managing all media for the fashion chain with significant focus on social, events and content development.
Betsaida Fernández Gómez, head of area media planning at Mango, said: "We are very excited to be working with Mindshare. They have the ability to deliver creative grounded in insight and have shown that they have a strong focus on client service and team work."
Jo Lyall, Mindshare partner, digital, said: "Mango is a fantastic client addition for Mindshare. There is an opportunity to do some really innovative work together and extend the reach of their core marketing campaign, using non-traditional services"
Mango, which employs Hollywood starlet Scarlett Johansson as its current celebrity face for campaigns, has nearly 1,500 outlets in 92 countries, with around 20 based in the UK.