Sarasaeschna pryeri Martin, 1909 (Aeshnidae, Odonata), which is distributed in Japan and the Republic of Korea is a rare species that has been found exclusively on Jeju Island in the Republic of Korea. Even though more information has been required to better understand the ecology of the species, research on this species has been limited mainly due to local distribution and rarity. Following recent observation on its occurrence in the Korean peninsula areas, this study evidenced the inhabitation of S. pryeri in the mid-eastern region of Korean peninsula in Gangwon Province in the Republic of Korea. In detail, throughout two years’ f ield investigation, adults and nymphs were detected in four Korean peninsula locations, such as Yachon-ri, Jukwang-myeon; Haesang-ri, Ganseong-eup; Gajin-ri, Jukwang-myeon; and Unbong-ri, Toseong-myeon in Goseong-gun in Gangwon Province. Moreover, observations of ecological behavior, in particular for oviposition activities, confirms the inhabitation of S. pryeri in Gangwon Province. In order to substantiate species status, we provided the description of adult and nymph morphology, and molecular identification. The ecological and behavioral information obtained in this study can serve as crucial foundational data for the understanding the ecology of d...