Republic won the business following a pitch against its fellow roster agency Modem Media.
It will now deliver an online advertising campaign for BBCMundo.com, the 24-hour news service website, to run across the US, Argentina, Mexico and various countries in Latin America.
The campaign is scheduled to launch in September.
Gavin Marshall, the business director at Agency Republic, said: "People in Latin America are heavy consumers of news and online news sites, particularly from local newspapers. That, combined with the political environment across the various countries, makes this a challenging and fascinating brief."
The account is the third BBC brief Agency Republic has won since it was appointed to the roster in April 2005.