Trade negotiator David Walker is to be a deputy secretary at the Foreign Affairs and Trade Ministry.
Dr Walker would have responsibility for the Americas, Asia, the Middle East and Africa starting next April, ministry chief executive John Allen said in a statement.
Dr Walker is New Zealand's Ambassador and Permanent Representative to the World Trade Organisation (WTO) in Geneva and is also chairman of the Doha Round agriculture negotiations.
Mr Allen said Dr Walker would remain in Geneva until Easter next year to provide leadership to New Zealand's Doha Round negotiating effort and to guide the agriculture negotiations.
"The process to appoint a replacement for Dr Walker as New Zealand's WTO Ambassador will start shortly."
WTO members would decide who the new chair of the agricultural negotiations would be.
Dr Walker led New Zealand's negotiations with China that created the NZ-China Free Trade Agreement. He was also the lead negotiator for the P4 trade agreement between Singapore, Chile, Brunei and New Zealand - the precursor to the current Trans Pacific Partnership negotiations.
Dr Walker has also been the ministry's principal economic adviser, worked in Washington as deputy chief of mission and was director of Apec division when New Zealand chaired Apec in 1999.