Background: The purpose of this study was to compare the self- efficacy, self -esteem, social anxiety, shyness and aggression among the high school students with different levels of assertiveness.

Materials and Methods: In this study, 311 first and second grade high-school students were selected from the five regions of Tehran (North, South, Central, East, and West) through cluster sampling. The low, high and moderate-assertive participants were recognized based on the mean and standard deviation of assertiveness. Multivariate analysis (MANOVA) was used to compare the research variables in the three groups.

Results: The results showed a significance value of F for Wilks lambda (F=4.12, P=0.001) indicating the overall differences in different levels of assertiveness. There was a significant difference in self-efficacy (P<0.001, F: 13.77) and self-esteem (P<0.001, F: 4.80) in three groups of assertiveness. Moreover, a significant difference was found in aggression (P<0.001, F: 12.1), social anxiety (P<0.001, F: 5.24) and shyness (P<0.001, F: 8.65) among the high, low and moderate-assertive students.

Conclusion: According to the results of this study, the high-assertive students had the higher levels of self-efficacy and self-esteem and lower levels of social anxiety, shyness and aggression as compared to the low and moderate-assertive students.