Lasionycta secedens is a moth of the family Noctuidae. It has a Holarctic distribution. North American populations are distributed from Labrador, northern Manitoba, and Alaska, southward to northern Maine, northern Minnesota, and south-central British Columbia. Subspecies bohemani occurs in northern Eurasia, Alaska and Yukon.
It is found in boreal forest, especially bogs, and is both diurnal and nocturnal.
Early instar larvae prefer to feed on the epidermis of leaves of Vaccinium vitis-idaea, but is polyphagous when reared. In Scandinavia the larva overwinters twice. In Minnesota this species occurs in raised bogs with Vaccinium vitis-idaea suggesting that this is the foodplant in North America.