As the European chief executive, the former Walsh Trott Chick Smith founding partner and WCRS managing director will be responsible for increasing synergy among 22 offices across the continent and boosting new business.
Although her role is a new one, she will take over many of the responsibilities of Lee Daley, who announced in January that he was quitting as the global chief executive of the WPP-owned operation.
Walsh's arrival in May completes an almost totally new senior management line-up at Red Cell, following the appointment of Laurence Mellman, a former WPP senior manager, as the network's chief operating officer.
Walsh, 45, will report to Andy Berlin, the founder of the Red Cell-owned Berlin Cameron agency in New York and the network's newly appointed chairman and chief executive.
One of her main objectives will be to boost co-operation between Red Cell's flagship agencies, Berlin Cameron and Britain's HHCL/Red Cell, and to work with the New York agency to bring more US business to Europe.
At the same time, she has been briefed to develop strong Red Cell offices in key European markets.
She must also assimilate 15 former Bates offices in Scandinavia, Holland, Belgium, Austria and eastern Europe that have been subsumed into the Red Cell network after WPP's takeover of Bates' Cordiant parent.
"Red Cell has some very good creative agencies but there's not been much attempt to build a culture," Walsh said. "It needs to be pulled together and given some focus."
Walsh takes on the job after discussions with Berlin and WPP's group chief executive, Sir Martin Sorrell.
Berlin said: "Red Cell has committed to expansion in Europe, so experienced leadership is crucial to our success. Amanda's very special presence, her experience with clients and as a manager will ensure that our client-facing offer is on the mark."
Walsh, who rose through the WCRS ranks to become the head of account management and new business, vowed to take a complete break after leaving Walsh Trott, which she helped found in 1995.
"I'd looked at jobs outside advertising but found that wasn't really what I wanted to do," she said. "I knew nothing about Red Cell but I've since discovered that it's almost like a start-up that is full of entrepreneurial people. It feels very uncorporate."