Head of UK corporate affairs Nick Hindle said Casofsky's role would include the handling of Ofcom's review of advertising to children, nutrient profiling, and McDonald's efforts to be recognised as a socially responsible brand and a good employer.
He will work alongside the company's retained agency, Bell Pottinger Public Affairs.
Casofsky replaces Caroline Weber, who now works in the firm's European corporate relations team. Before Finsbury he was parliamentary assistant researcher to ex-Labour MP Alan Hurst.
His arrival completes a triumvirate reporting to Hindle, alongside head of media relations and internal comms Amanda Pierce and head of sports sponsorship Stephen Hall.