Typhoon Dujuan brought heavy rains to the province after lashing neighbouring Hong Kong earlier this week.
At least 20 of the fatalities occured in Shenzhen city, while nine others died in Huizhou city. Many of the deaths occured when poorly built structures, especially shacks used to house migrant workers, collapsed.
The typhoon was the most damaging to hit Guangdong's Pearl River Delta since 1979.
China's official Xinhua news agency said that 16 migrant workers on a construction site were among those killed. It gave no details.
The storm cut power and water supply in the city of Shanwei and in some districts of Shenzhen, directly across the border from Hong Kong.