During World War I (1914–1918), Brazil initially adopted a neutral position, in accordance with the Hague Convention, in an attempt to maintain the markets for its export products, mainly coffee, latex and industrial manufactured items.

However, following repeated sinking of Brazilian merchant ships by German submarines, President Venceslau Brás declared war against the Central Powers in 1917.

Brazil was the only country in Latin America to be directly involved in the war. The major participation was the Brazilian Navy's patrol of areas of the Atlantic Ocean.