The ongoing brief makes Tin Man responsible for all creative UK-wide PR campaigns and press office activity for The Balvenie, Monkey Shoulder, The Girvan Patent Still, Hudson, Kininvie, Rare Cask Reserves and new brand, Ailsa Bay.
The win follows a pitch involving 10 agencies, and was previously held by Anonymous Artists.
Jonathan Cornthwaite, senior brand manager at William Grant, said: "We needed a PR partner that we felt could significantly grow awareness of our brands, support our existing marketing activity and add creative and strategic value across the portfolio."
Other brands owned by William Grant include Glenfiddich whisky, Hendrick's gin and Tullamore DEW. Irish agency Thinkhouse took on global PR for the latter in November.