This study aimed to test whether assertiveness is a mediator between academic self-efficacy and popularity, and whether social preference would have a moderating effect on the mediation of assertiveness. The participants consisted of 789 students, including 512 girls and 277 boys, selected from four high schools located in a city centre in the Central Anatolian region of Turkey. The participants were 9th-12th-grade students in 34 different classes. The average age of students was 15.40. This research was a cross-sectional design. Model 4 was used to examine the mediating effect, and Model 5 was used to test the conditional indirect effects in Process Macro. Findings showed that the effect of academic self-efficacy social status on popularity is partially mediated by assertiveness. On the other hand, assertiveness fully mediated the association between academic self-efficacy technical skills and popularity. Moreover, the mediating effect of assertiveness on the association between academic self-efficacy and social status, academic self-efficacy technical skills and popularity is moderated by social preference levels.