Animal bones excavated from historic sites provide valuable data for identifying the lifestyles of people and the distribution of animals at that time. In this study, we investigated the morphological structure, size, and measurements of Cervidae bones excavated from a well at the Gasan-ri archaeological site in Jinju, which are believed to be relics from the Three Kingdoms period. The total number of excavated animal bones was 447, of which 102 (22.82%) were classified as Cervidae bones. The weight of Cervidae bones was 453.79 g, accounting for 46.53% of the total weight of the identified bones (975.30 g). The Cervidae bones were identified as those of two animals with an estimated age of 5–6 months. The Cervidae bones are divided into skull bones, vertebrae, ribs, sternum, hip bones, forelimb bones, and hindlimb bones. The 102 Cervidae bones consisted of 19 skull bones (18.63%), 14 vertebral axial skeletons (13.72%), 28 ribs and sternum (28.43%), 16 forelimb bones (15.69%), and 19 hindlimb bones (18.63%). The remaining six were difficult to distinguish. A fracture of the parietal bone located near the bregma of a skull was observed and was presumed to have been caused by an artificial blow. This study can be used as basic data to estimate the types of animals and human culture at the time through Cervidae bones believed to be relics from the Three Kingdoms period.