The brief involves promoting the offering at World Duty Free, with a particular focus on beauty and liquor goods.
Unity won a pitch for the account in June 2013.
Mischief associate director Charlotte Dolman will lead the account and will report to Karen Sharpes, senior PR manager at World Duty Free Group.
Sharpes said: "Mischief fully understood what we’re trying to achieve as a business. With its inventive and creative thinking, we believe we can achieve our goals. We look forward to working together on some truly innovative work."