The northern beardless tyrannulet is  long, and weighs . The head is dark brown with an erectile crest and pale supercilium. The upperparts are grey-green becoming paler on the rump.
The northern beardless tyrannulet measures  long, and has a weight of . Its head features a dark brown color with an erect crest and pale eyebrow stripe. The upper body is grey-green in hue, gradually becoming lighter towards the rump.