The purpose of this study was to assess the mediating effect of self-efficacy on the relationship between identity styles and academic achievement. Four-hundred high school students (200 male, 200 female) who were selected through cluster random sampling, completed the Revised Identity Styles Inventory (ISI, 6G) and Morgan-Jink Student Efficacy Scales (MJSES). Path analysis was used to analyze the data. In general, the results indicated that informational identity style had a positive direct impact on academic achievement, while diffuse/avoidance identity style had a negative effect on academic achievement. Data also suggested that informational and normative identity style had a positive influence on academic achievement through the mediation of academic self-efficacy.