Callewaert's mouse is a large-bodied African pygmy mouse with forward-pointing incisors. It has been recorded in Angola, the Democratic Republic of the Congo, and Malawi.
It is described as the largest species in the African subgenus Nannomys, with proodont, forward-pointing incisors. It is relatively large-bodied with a shorter tail and reddish fur.
It has been captured in grassy places, including locally moist sites. The authors hypothesize an insectivorous diet but state that it needs further testing.
An extinction-risk assessment has not been added yet.