According to the 2007 census, 9524 people were living in the tabia, which results in a population density of 68 inhabitants per square kilometer.
Dergajen is located on the hydrographic divide between the Tekeze catchment in the west and the endoreic Afar basin to the east.
The following geological formations are present in this locality:[4] The main geomorphic unit, with corresponding soil types is:[8] The area gets relatively larger quantities of precipitation, due to its location on the eastern edge of the Ethiopian Highlands.
With an area of approximately 139 square kilometers, Dergajen used to be a district of the Enderta province already in Imperial times.
In those times, Qwiha functioned as administrative center for the district Dergajen, while Mekelle was the capital of the Enderta province.