U.N. Secretary-General Ban Ki-moon inaugurated the account from New York with a video message broadcast on WeChat and other online social media, China's state-run news agency Xinhua reported.
"I hope that this U.N. WeChat will enable many Chinese citizens to understand the latest news and information about what we are doing and why it matters," Ban said.
WeChat, a popular mobile social networking platform developed by Chinese tech company Tencent, offers voice messaging and information sharing services. The company said it has 300 million registered users since launching in 2011.
The U.N. WeChat launch came ahead of Ban's four-day visit to China beginning Tuesday.
The account will be managed by the U.N. Public Information Department at its New York Headquarters, Xinhua said.
Chinese officials said the official U.N. Weibo account -- China's microblogging platform similar to Twitter -- soon will pick up its 4 four millionth follower.
Xinhua said a certificate commemorating the milestone will be presented during the secretary-general's visit.