The White-tailed Tyrannulet searches for insects in the canopy of humid Andean forest. White inner webs of the tail feathers and pale wingbars help identify it.
The mantle is olive-green and the underparts are mostly greyish. The wings have two buffy bars, and white inner webs of the tail feathers show from below or when the tail is spread.
It searches for insects in humid montane-forest canopy and sometimes forages with mixed-species flocks.
The head is grey, with a broad white eyebrow stripe and a black bill.
An extinction-risk assessment has not been added yet.