The account win will see Citizen creating a digital-first, global communications strategy and content programme as part of a new long-term platform for the brand.
PR and comms activity will be rolled out to The Macallan’s chief global markets in Asia, Europe and The Americas.
Citizen will work in partnership with a fully integrated agency team, which includes J.Walter Thompson London, who was chosen as global creative agency earlier this year.
"Citizen has an impressive track record in multi-market, equity-building brand campaigns so we are delighted to be working with this team of experts," The Macallan global marketing controller Paul Condron said.
"With their strong understanding of our current and future aspirations, we look forward to working in close partnership during this exciting period and beyond."
Helena Fisher, MD of Citizen Relations London, said: "We are thrilled to be working with such a luxury whisky icon. The Macallan’s unique combination of unparalleled heritage, inherent future-thinking and uncompromising quality across the board makes it the dream client partner, so we are delighted to be on board."
The Macallan is the third-highest selling single malt scotch whisky brand in the world – with 907,000 cases sold in 2017 – behind Glenfiddich (1.22 million cases) and The Glenlivet (1.07 million cases).
It is also famed for fetching the highest price for a single bottle at auction. This year, The Macallan Valerio Adami 1926 60-year-old sold for £848,000 at auction in Edinburgh.