A passport and visa are required for U.S. citizens traveling to Brazil for any purpose. Brazilian visas must be obtained in advance from the Brazilian Embassy or consulate nearest to the traveler's place of residence. There are no "airport visas" and immigration authorities will refuse entry to Brazil to anyone not possessing a valid visa. All Brazilian visas, regardless of the length of validity, must initially be used within 90 days of the issuance date or will no longer be valid.
U.S. citizens reentering Brazil must be able to show an entry stamp in their passport proving that the visa was issued within 90 days; otherwise they will not be allowed reentry. Immigration authorities will not allow entry into Brazil without a valid visa. The U.S. Government cannot assist travelers who arrive in Brazil without proper documentation.
Additionally, travelers who have recently visited certain countries, including most other Latin American countries (check www.brasilemb.org), may be required to present an inoculation card indicating they had a yellow fever inoculation or they may not be allowed to board the plane or enter the country.
Please note that non-U.S. passport holders are responsible for obtaining the required documentation applicable for their entry.