Oscar, Hernanes and Lucas scored the goals in the second half as Brazil claimed a first win over Les Bleus in 21 years and condemned the French to a third straight defeat.
Deschamps' men have now lost to Germany, Spain, Uruguay and Brazil this year with just a solitary win over Georgia in March standing out on the calendar.
France's next assignment is a friendly against Belgium in August before World Cup qualifiers in September and the former Marseille boss knows his team must improve.
He told reporters after the game: "You can make mistakes, but can't afford to lack commitment. We had neither the head nor the legs for this match, and so we finish our mini-tour with two defeats.
"We played well for 20 minutes against Uruguay and also for a time against Brazil.
"Our objective remains qualification for the 2014 World Cup. But even in adversity, when we're playing against superior opposition, we have to be able to do better than we have done."
After a 1-0 defeat to Uruguay on Thursday night, France also end their South American tour without a goal and striker Karim Benzema could not hide his disappointment following another defeat.
"Even though it was a friendly, we're all competitors," he said. "We're all disappointed.
"In the first half, we had a few chances, but we couldn't convert. After that, bit by bit, we floundered.
"In the second half, we had nothing to speak of. I don't know whether we gave up or not, but we certainly gave the impression of having run out of gas.
"We got pushed back after the first goal and then conceded another two.
"It's always tough to lose, but 3-0 is hard to take. It was a horrible match. But you can always get worried after losing a game.
"Now we're off on holidays and we'll have a chance for a good rest.
"In September, we can't afford to miss our chance."
Brazil now look forward to their Confederations Cup opener against Japan on Saturday and manager Luiz Felipe Scolari believes they still have much to work on.
"We have to keep working so we can reach the World Cup with a competitive team," he said. "A team organised to win matches. This is happening slowly.
"This was the first week that the whole group worked together. Now we'll have another week until the opening match against Japan. We'll fix some minors errors so our players will be in their best shape. We'll add on what we did today against France.
"We needed this extra push from our fans to give this huge leap against such a big team as France and now we can focus on winning the Confederations Cup."