A motorist said he lost control of his car as it drove onto the crowded seaside promenade along Copacabana Beach in Rio de Janeiro injuring 15, police said.
Brazilian military police said in a statement there was no indication that the incident was a terrorist attack.
Several European and American cities have seen terrorist attacks in which drivers ploughed into crowds.
Police have arrested the driver, who told them he had not been drinking but had lost control of his car.
He also said that he suffered from epilepsy, according to the police statement.
The promenade along Copacabana beach was crowded with people on the hot summer night when the car jumped over the kerb.
A witness reported seeing at least one child among the injured, many of whom were knocked down and were treated initially where they lay on the ground.
The car stopped in the sand after it apparently crossed the wide pavement that runs between the beach and a busy road.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here