Brazil is enormous and varied. A card-first day in São Paulo and a cash-heavier stop in a remote region can both be normal. The useful response is a layered wallet, not a large wad of “just in case” cash.
Split the trip into three pockets
Use the ATM's location as a security feature
Official travel advice recommends machines inside secure facilities such as a bank, airport, hospital or government building rather than an isolated street location. Daytime and a staffed environment give you options if the card is retained or the cash looks wrong.
Keep the card and amount in view
Card cloning and incorrect terminal amounts are reported risks. Let the merchant bring the portable machine to you, keep sight of the card, verify the digits and ask for a receipt. A contactless tap reduces handling but does not replace checking the screen.
Low notes solve more than large ones
R$ 5, 10 and 20 notes handle small snacks, tips and cash-only gaps without exposing a large reserve. R$ 50 is a useful bridge. Treat R$ 100 and R$ 200 as reserve values to break deliberately, not automatic street-wallet inventory.
A phone can be part of the wallet
Banking and Pix access on a phone make the device financially powerful. Use a strong screen lock, lower transfer limits where your provider allows it and avoid reviewing banking apps in an exposed street setting. Keep the provider's emergency contact somewhere outside the phone.
Large cash crosses a legal line
Brazil's Federal Revenue requires an electronic traveller declaration when entering or leaving with more than USD 10,000 in cash or the equivalent in another currency. An ordinary holiday wallet should be nowhere close, but the rule matters for long trips, group funds and valuables.