In Korea, 104 species of Notodontidae have been recorded. The genus Odontosia H$ddot{u}$bner is characterized by the elongate and serrate margin of its forewing and the prominent harpe of valva and many spinular cornuti on the vesica of the male genitalia and the robust ductus bursae and large, ovate and sclerotized corpus bursae of the female genitalia. Only one species of Odontosia, O. patricia Stichel, 1918, has been reported from Korea. In this paper, Odontosia sieversii ($Macute{e}nacute{e}trigrave{e}s$, 1856) is newly added to the Korean fauna based on three male specimens collected at Mt. Bangtaesan, Gangwon-do, Korea. Diagnosis for the species and photographs of adult and genitalia of the genus Odontosia are provided.