Edelman said Reddick will oversee creative production within the corporate reputation team, working with the agency’s creative network.
At The Moment, Reddick worked on campaigns for brands including Vodafone, Audi, Kenco, Continental Tyres and Channel 4.
Nick Barron, UK MD of corporate and financial at Edelman, said: "Edelman’s work is focused on helping clients engage their audiences directly, through their own channels and platforms, but the content marketing landscape is incredibly cluttered and most brand-produced content is just noise. Ryan will help our clients tell genuinely interesting and inspiring stories."
Reddick, who joins the agency later this month, said: "This is an opportunity to work with a world-class roster of clients, as part of a firm that specialises in building trusted relationships."
Reddick is one of a number of new senior hires at Edelman UK & Ireland recently, following the likes of Will Walden, Boris Johnson's former adviser and comms director, as MD of its UK public affairs practice; Lucy Thomas, former deputy director of Britain Stronger in Europe and former BBC producer; and James Morris, previously a director of polling group Greenberg Quinlan Rosner and former adviser to ex-Labour leader Ed Miliband.
Earlier this week, Edelman reported organic revenue growth of 1.7 per cent in 2016, which it described as a "transition year" for the world’s biggest PR agency.
Global CEO Richard Edelman said business in the UK "held up better than we expected in the wake of Brexit", adding: "Clients didn’t pull budgets, the London office performed quite well."