The board of regulator Cade unanimously approved a proposal to fine Morgan Stanley 30.280 million reais and RBC 12.586 million reais.
The banks are accused of colluding to manipulate spreads between bid and ask rates on offshore spot-market transactions involving the Brazilian real.
Cade had already fined Barclays Plc, Citigroup Inc, Deutsche Bank, HSBC Holdings Plc and JPMorgan Chase & Co 183.5 million reais in 2016 as part of the investigation.
(Reporting by Bruno Federowski; Editing by Richard Chang)