Buttress and Davies will be associate directors.
Buttress will join the agency in May from Tesco where she heads up consumer PR. Before this she worked at Travelex.
Davies has been at The Red Consultancy for eight years, working on technology accounts including Samsung and Activision.
At Mischief, Davies will head up a range of lifestyle and tech brands, such as Lynx and The Walt Disney Company. Buttress will work on the agency’s homes and interiors sector, with clients including Dulux.
Davies said: "This agency has a proven track record of outstanding work and results – and I’m looking to forward to adding to that success."
Both will report to CEO Frankie Cory, who said: "Freddy and Jess bring the expertise and passion to deliver convention-rocking work that's both creative and commercially impactful."