In March, the popularity of the government reached a record high of 63 percent before slumping to 55 percent ahead of the June protests, according to the Ibope survey commissioned by the National Industry Confederation.
Rousseff's own standing sank from 71 percent in early June to 45 percent today, a little over a year before scheduled national elections.
The poll showed that the protests, called to denounce endemic corruption and demand better public services, also dragged down the popularity of many mayors and state governors, including in Sao Paulo and Rio de Janeiro states.
The poll of 7,686 respondents was conducted from July 9 to 12 and has a margin of error of two points.
Last week, another survey by the MDA polling institution also pointed a sharp drop in Rousseff's popularity, with 49.3 percent support and 47.3 percent disapproval.