This study aimed to verify the validity of Levels of Personality Organization (LPO) using the Social Cognition and Object Relations Scale - Global rating method (SCORS-G) global score ratings of the Thematic Apperception Test (TAT) narratives in nonclinical samples and explore methods of its application. The TAT (1, 2, 3BM, 4, 13MF, 12M, 14) and various scales measuring psychopathological, interpersonal, cognitive and emotional problems were administered to 215 undergraduates and 138 high school students. TAT protocols were then rated with SCORS-G. Participants were classified into three LPO groups based on their overall SCORS-G composite rating. Differences of various psychological and personality functioning were analyzed among three groups categorized according to LPO. As a result, in both the university student sample and the high school student sample, there were significant differences in various psychopathologies, personality traits, and maladaptive problems among different LPO groups. Also, the performance-based theory of mind task was administered only to the university student sample and a significant differences according to LPO were found in its performance levels. In the university student sample, as LPO ascended by one level, the degree of psychopathologies and maladaptive psychological problems decreased, whereas the stability of personality traits and the accuracy of the theory of mind increased. In the high school student sample, it was found that LPO 2 and 3 showed better levels than LPO 1 in psychological and personality domains. These results suggest that the SCORS-G can be appropriately used in the evaluation of LPO. Furthermore, this study discusses how to utilize and interpret SCORS-G in assessing LPO by connecting the empirical results with theoretical LPO.