Taczanowski's oldfield mouse is a medium-sized rodent recorded in montane forests of Ecuador and Peru. Its fur is soft, and some individuals have a white tail tip. Ecological observations are limited.
The fur is soft and woolly. The back is grayish yellow with rufous-tipped hairs, and the underside is grayish white. The tail is pale brown and may have a white tip.
Ecological records are sparse. The species has been caught in tall shrubs and small trees in upper montane forest and in Polylepis woodland. Field observations suggest that it may be an agile climber.
An extinction-risk assessment has not been added yet.