Thirteen water-bombing helicopters joined around 350 firefighters spread across 150 hectares (370 acres) in the Saxon Switzerland National Park, district authorities said.
Four firefighters have sustained minor injuries, they added.
Rain showers on Saturday were not enough to keep the flames at bay.
The fire broke out on Sunday last week in the neighbouring Czech Republic before spreading to Germany.
A fire in southern Brandenburg, also in the country’s east, is now under control, local authorities said. It prompted the evacuation of around 700 people earlier this week.
Scientists say climate change is making heatwaves around the world more frequent and more intense, increasing the risk of fires.