Hundreds of thousands of Brazilians took to the streets during the warm-up tournament in June, demanding better public services and expressing their anger over the costs to stage the World Cup.
"If this happens again we have to question whether we made the wrong decision awarding the hosting rights," Blatter told German press agency DPA on Wednesday.
FIFA spoke with the Brazilian government after the Confederations Cup, and Blatter said he'll discuss the issue again with Brazil President Dilma Rousseff in September.
"We didn't do a political debriefing, but we did emphasize the fact of this social unrest being there for the entire duration of the Confederations Cup," he said. "The government is now aware that next year the World Cup shouldn't be disturbed.
"To me, these protests were like alarm bells for the government, the senate, the parliament. They should work on it so that this is not going to happen again. Though protests, if peaceful, are part of democracy and therefore have to be accepted ... we are convinced the government, and especially the president, will find the words and the actions to prevent a repeat. They have a year to do so."
Blatter was speaking at the start of a two-day conference on sports, media and economy set up by German great Franz Beckenbauer in Austria. FIFA later verified the comments were accurate.
The Confederations Cup, which was won by Brazil, angered citizens who are upset with the billions of dollars spent on the tournaments while they endure underfunded schools and hospitals.
Protesters aired a wide spectrum of grievances, including the high cost of hosting the 2016 Rio Olympics.
The protests were originally organized by university students before spreading across the country, including tournament host cities Brasilia, Rio de Janeiro, Salvador, Fortaleza and Belo Horizonte.
"It's not we who have to learn lessons from the protests in Brazil — politics in Brazil have to do that," said Blatter, adding that "FIFA cannot be held responsible" for social discrepancy in the country.
Without FIFA's executive committee having to vote, Brazil won the right to host the tournament in October 2007. That was six months after the only other candidate, Colombia, withdrew its bid.
"The decision for Brazil was the best decision we could make. It was the correct decision, we stick to this decision," Blatter said.
Blatter said the success of next year's tournament will be instrumental in his decision whether to stand for president for a fifth time in 2015, adding that not all of the governing body's tasks have been fulfilled yet.
"First we have to complete the reforms, which are three-quarters done. I'll then have to deliver the World Cup ... the way the world looks now, I'll say yes or no (to standing again) at the next congress in Sao Paulo in 2014," he said. "FIFA should be taken over by someone who can take over a FIFA which is not just financially healthy, which it is now, but which also has credibility."