The district consists of lowland forest, and highland grasslands.

[2][1]: 3 In 2016 the Tanzania National Bureau of Statistics report there were 468,679 people in the district, from 425,794 in 2012.

The largest ethnic groups are the Waha, Wahaya, and Wasukuma tribes.

[5][6] The main economic activity is subsistence farming and small and medium-scale businesses, especially in Kasulu town.

There are a few "Wasukuma" ethnic group pastoralists who come into Kasulu with flocks of cattle in search of pastures.