The Inter Milan star - considered by many to be the best goalkeeper on the planet - complained of a back injury and had to be replaced by Heurelho Gomes after just 26 minutes in Harare.
He was inspected by team doctor Jose Luis Runco after falling awkwardly in the 19th minute and deciding to come off as a precaution.
Worry: Julio Cesar was injured in Brazil's warm-up match against Zimbabwe
Sources say they do not believe the injury to be serious, but it will still worry the coach on a day that his side won 3-0 with goals from Michel Bastos, Elano and Manchester City exile Robinho.
Dunga's second-choice is generally Roma's inconsistent and out-of-favourkeeper Doni. However, Tottenham Hotspur keeper Gomes was sent on and impressed with a series of saves against a Zimbabwe side that included Manchester City striker Benjani.
Heart-stopper: Kaka lies injured during the match in Harare
Kaka, who has been struggling for fitness and form, was also floored by a heavy tackle but was able to get up and continue before being replaced at half time by former Arsenal midfielder Julio Baptista.
Brazil's first match at the tournament is not until June 15, when they face North Korea in Johannesburg. The five-time champions also face Ivory Coast and Portugal in the tricky Group G and will hope to have Julio Cesar between the posts.
Practice makes perfect: Luis Fabiano (right) celebrates with goalscorer Robinho
Zimbabwe president Robert Mugabe made the most of Brazil choosing Harare for their first World Cup warm-up match.
The controversial leader gave workers half a day off an waved to the packed stadium from the side of the pitch before the match.
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