"We think we will have to intensify the security monitoring system. We will have to increase the number of checkpoints and controls," Defense Minister Raul Jungmann told TV station Globo.
Interim president Michel Temer's office said he would meet with his intelligence chief and defense and justice ministers at 4:00 pm in response to the Nice attack, which killed at least 84 people.
The attack, perpetrated with a 19-tonne truck, showed that "any tool, any instrument, any vehicle can be the vector of a terrorist act," said Jungmann.
The head of the intelligence service, Sergio Etchegoyen, said fears over security at the Rio de Janeiro Games, which open on August 5, had "gone up a notch" after the attack in France.
He said new security measures would include extra checkpoints, barricades and traffic restrictions.
"We're trading a little comfort for a lot more security," he told a press conference at the presidential offices.
Brazilian intelligence officials met with French counterparts on Friday for a briefing on the Nice attack, he said.
The French resort city is in shock after a Tunisian-born man drove a white truck into a huge crowd gathered to watch the annual Bastille Day fireworks display, leaving a gruesome trail of bodies in his wake.
The attack triggered new fears in Brazil, already on alert after the French military intelligence chief said France had been informed of a planned terror attack on its team at the Rio Olympics.
In June, Brazil's intelligence service said it had detected Portuguese-language messages linked to ISIS on an online forum.
An even more explicit warning came after Islamist attacks in Paris last November, when a French jihadist tweeted that Brazil was the "next target."
Brazil plans to deploy 85,000 police and soldiers to provide security for the Olympics -- double the number used in the 2012 London Games.