The Arfak Mountain Leptomys is a medium-sized rodent with a dark brown mid-back, buffy-brown flanks, and white fur from the chin to the base of the tail. The 2017 account reports two known specimens collected in the Arfak Mountains in 1925.
The mid-back is dark brown and the flanks are buffy brown. The underparts are pure white from the chin to the base of the tail. Dark masks surround the eyes.
The two known specimens were collected in 1925, and the HMW account places their capture locality at 1,000 m, close to the transition between hill forest and lower montane forest. This describes the capture site; it does not establish a preferred forest type or a wider habitat range.
An extinction-risk assessment has not been added yet.