St. James' Palace said the 27-year-old prince will visit Rio de Janeiro and Sao Paolo from March 9 to 11.
The trip comes after Harry tours Belize, the Bahamas and Jamaica in the first week of March on behalf of Queen Elizabeth II as part of her Diamond Jubilee celebrations.
The palace said that it would be the first time the prince visited any of the countries.
The Brazil tour is organized by Britain's Foreign Office, but Harry will stay on privately until March 14.
The Associated Press contributed to this report.