Objectives The study aims to explore how high school students’ perceived self-esteem and grit mediate the rela-tionship between peer relationships and career adaptability while also examining whether there are any differ-ences in the relationships between variables depending on gender.
 Methods The data from the Children and Youth Panel Survey (KCYPS) 2018 conducted by the Korea Youth Policy Research Institute was used to analyze the data collected from 1,217 male students and 1,048 female students in their first grade of high school. SPSS and PROCESS Macro programs were used to analyze the data and inves-tigate the relationships between variables using a dual mediation model analysis. In addition, to verify the differ-ences according to gender, the analysis was performed by dividing the male and female groups and comparing the results.
 Results Peer relationships positively affected career adaptability in both male and female groups. In both genders, the paths of peer relationships affecting career adaptability through self-esteem and peer relationships affecting career adaptability through self-esteem and grit sequentially were significant. However, while the path of peer relationships affecting career adaptability through grit was significant in the male group, it was not significant in the female group.
 Conclusions This study focused on the result that positive relationships with peers contribute to positive evalua-tions of themselves and also grit, thereby affecting career adaptability. This study also yielded gender differences in how peer relationship affects career adaptability. Based on the results, suggestions for career guidance practice were dealt on how to utilize peer relationships.