George Abu al-Zulof, the head of the UN human rights office in Yemen, "has been doing an excellent job," spokesman Stephane Dujarric said.
The decision came just days after the United Nations raised alarm over the use of cluster bombs by the Saudi-led coalition backing Yemen's government in its war against Shiite rebels.
The office of the UN high commissioner for human rights said on Tuesday that its staff in Yemen had found remnants of 29 cluster bombs during a field visit in Haradh district in the northwest.
The United Nations has been increasingly concerned by the mounting civilian toll in Yemen and the dire humanitarian crisis.
Yemen descended into chaos when the coalition began air strikes in March to push back Huthi rebels who seized in the capital Sanaa in September.
At least 2,795 civilians have been killed since March.