The brands involved are Sprite, Fanta and Ayataka, a bottled green tea. The pitch took place over the last few months and was decided about three weeks ago.
The incumbent, UM, as well as Dentsu and Hakuhodo took part in the pitch, according to sources.
A source places the value of the accounts at as much as $60 million. MediaCom takes over the account on 1 August.
The agency won Coca-Cola in Vietnam in August 2013. Prior to that, MediaCom was named agency of record for Indonesia and Myanmar In 2012, and in Singapore and Malaysia in 2011.
Campaign Asia-Pacific offered UM, Dentsu and Hakuhodo the opportunity to comment.