Carr is currently chief operating director at the Waterfront Partnership, which was this week sold to the AIM-listed group Freshwater.
Waterfront was acquired for a maximum consideration of £2.24m, some of which is deferred and contingent on future profits. The price includes a mixture of cash and shares.
Before joining the Waterfront Partnership, Carr spent eight years at Bell Pottinger Public Affairs, rising to the role of director.
He will be joining Southwark-based Madano in the new year, taking the title of partner.