Buonaiuto joins Weber Shandwick from the Purpose Foundation, where he was creative lead, and will oversee the film and the agency's animation production department.
He will also be responsible for the online paid content distribution arm of the business.
Buonaiuto will report to Ian Cohen, who leads Weber Shandwick’s content production business globally.
Cohen said: "To have someone with Mike's background on our global studio team makes sure content can drive the story for our clients across all platforms."
The Digital Studio is Weber Shandwick’s in-house production facility that creates graphic design work, videos, apps, websites and animations for clients.
Among Buonaiuto's best-known work is Homecoming, which he made while at Nüko, a division of the Remarkable Group, for the Coalition for Equal Marriage.
The film won Best Use of Online Video at the London Digital Impact Awards 2012.