The 55-year-old Romanian takes over from Portuguese Paulo Bento, who was fired last month despite a last-gasp win over North Korea in Asia's World Cup qualifiers.
The UAE are third in Group A of the preliminaries for the 2026 finals in the United States, Canada and Mexico.
The first two finishers in each of Asia's three groups progress automatically to the World Cup while the third- and fourth-placed teams advance to another round.
Iran have already claimed one of the two berths available from Group A while second-placed Uzbekistan are four points clear of the UAE with two matches remaining.
Olaroiu has spent the last three-and-a-half seasons with UAE club Sharjah, and last week guided the team into the final of the AFC Champions League Two.
He has worked extensively in the Gulf region, coaching Al Hilal in Saudi Arabia, Qatar's Al-Sadd and the Emirati side Al Ain before moving to China, where he won the Chinese Super League title with Jiangsu Suning in 2020.
Olaroiu's first game in charge of the UAE will be their World Cup qualifier at home to Uzbekistan on June 5th. They then visit Kyrgyzstan in Group A five days later.
