Myotis frater is recorded from Fujian and Jiangxi in China and from Taiwan. In Taiwan it roosts in forest tree holes; in Fujian, specimens were collected from holes in live bamboo on mountains.
Its dense, soft fur is dark brown without gloss above and lighter creamy brown underneath. The wing membranes attach near the base of the outer toes, and the rear edge of the ear is notched.
In Taiwan, it roosts in forest tree holes. Lactating females have been recorded from June to August, depending on elevation. At Yenping in Fujian, three individuals were collected from holes in live bamboo stems in mountain habitat at about 760 m.
An extinction-risk assessment has not been added yet.