Akodon diauarum was described from dry forests in the Amazonia–Cerrado transition. Records in Brazil include seasonal forest and the ironstone outcrops of Carajás.
The back is dark brown with grey hair bases. The underside is dark grey-brown; some described specimens have a yellow or orange wash.
Most records are from seasonal deciduous forest in the Amazonia–Cerrado transition. At Serra dos Carajás it was also captured in ironstone outcrops, where it was more abundant than in adjacent forest.
An extinction-risk assessment has not been added yet.