This species generally has the appearance of a "scaled-down" (wingspan 38-48 mm) version of the Large Yellow Underwing. The forewings are equally variable, from light brown to almost black and it also has orange-yellow hindwings with a black sub-terminal band. The hindwings also have a black discal spot, usually absent from the larger species. It flies at night from July to September and is attracted to light and flowers such as heather, marram grass and ragwort.
The larva is also very similar to that of Large Yellow Underwing, green or brown with black dashes along the back. Its feeding habits, however, are very different: this is not a "cutworm" but feeds on the foliage of a range of plants, trees and shrubs as well as herbaceous plants (see list below). This species overwinters as a larva.