The Ibovespa fell 0.9% to close at 172,447 on Monday as investors awaited a public hearing in Washington on the US trade investigation into Brazil, which could lead to additional tariffs on Brazilian exports.
The hearing will consider a proposed 25% tariff after the USTR identified what it described as "unreasonable" trade practices.
Exporters led the declines, with Vale down 1.3%, Petrobras losing 1.3%, and Minerva slipping 0.8%.
Petrobras was also pressured by lower oil prices after OPEC+ agreed to raise output targets from August and shipping through the Strait of Hormuz continued to normalize.
Elsewhere, Ambev dropped 2.5% on concerns that third-quarter sales in Latin America could miss expectations after Brazil and Mexico were eliminated from the FIFA World Cup.