The London-based Droga5 Europe won the account after a competitive pitch against seven other agencies from the US and UK. It marks the first time that Farfetch has appointed a creative agency.
Farfetch has tasked the agency with creating a print, digital and experiential campaign across the business's key markets in a bid to become better known.
Stephanie Horton, the chief marketing officer at Farfetch, said: "Droga5 grasped our strategic challenges immediately and offered us a fully integrated creative solution that will help us to deliver on our 2015 marketing aims."
Farfetch, which is headquartered in London, launched in 2008 as a website where people can buy clothes from more than 300 independent fashion designers.
In May the company raised $66 million (£42.2 million) in a funding round that was led by Vitruvian Partners, with contributions from existing investors Condé Nast International and Advent Ventures.