One of the smaller Bryotropha species with a wingspan of 9 - 12.5mm. The forewing is quite variable in colour from pale straw-brown to dark brown and varies in having a fairly prominent angled subterminal fascia to no fascia at all. It lacks the contrasting paler forewing and dark heavy speckling of the similar sized B. basaltinella and B. dryadella and is brown rather than blackish distinguishing it from the dark form of B. umbrosella. B. senectella often has the a slightly darker line or band running through the middle of the head (vertex) in most, but not all individuals which contrasts with the paler cheeks. In dark forms, the usually pale yellow labial palpus and frons (which can be sprinkled with ochreous) may help distinguish it from the larger B. similis, which is creamy white in this area. Dissection is recommended with worn specimens or where the markings are obscure.
Darker forms might be confused with faintly marked or worn B. affinis but lack any hint of whitish yellow scaling around the central black spots. Generally B. affinis usually has a darker top to the head (vertex) but on occasions it can be creamy in colour. As a result, the darker line on the head of B. senectella, which varies in width and intensity, is best not used as a single identification feature.