Wingspan 15–20 mm. The imago is similar to some forms of Celypha lacunana. Orthotaenia undulana shows more discrete markings. It lacks the incision on the basal edge of the central band and the central lacuna. The distal edge of the central band may have a double projection or a single broad one when these are merged.
It may also resemble Celypha cespitana and Celypha rivulana but has no strong markings in the distal third of the wing.

The larva has a black head with brown mouthparts. The prothoracic plate is black or pitchy brown with a paler anterior border. The thoracic legs are dark brown or blackish. Full-grown larvae are dark reddish brown, but earlier instars may lack the reddish hue. The pinacula are coloured as the body, or a little darker. The anal plate is dark brown or black with an anal comb.

The larvae living between leaves spun together with silk. Pupation takes place in the larval habitation or a freshly spun leaf.
The adults are active from dusk onwards and later come to light.

The polyphagous larva lives between spun leaves of Lonicera, Vaccinium, Myrica, Betula, and a wide range of other trees, shrubs and herbaceous plants.

It inhabits many habitats like woods, gardens, moors, dunes, hedgerows, dry pastures etc...