Nielsen will become the creative partner to Erika Darmstaedter, who recently joined the team as global business leader. He will be part of the extended global leadership team in the UK and will be based in Hamburg.
At Saatchi & Saatchi, Nielsen was the regional creative director for Europe, Middle East and Africa for the agency's Head & Shoulders account for Procter & Gamble.
He has also worked at Leo Burnett and McCann Erickson as creative director, and more recently at JWT, BBH and BBDO.
Nielsen will report into Jonathan Harries, Draftfcb vice chairman and global chief creative officer.
Darmstaedter said: "Rob's experience working on global brands for such major marketers makes him the perfect addition to our newly strengthened global team.
"He has received numerous awards at prestigious ad festivals including Cannes, D&AD, IPA Effectiveness Awards and Eurobest and I know he's going to bring this outstanding creative ambition to the account."
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