Objective: The aim of current investigation was studying the relationship among assertiveness, self- esteem, and academic achievement in gifted and regular school students. Comparing regular school students and gifted students in these variables also were studied. Method: In this study expos facto (causal-comparative) design was utilized. sixty gifted students (30 girls, and 30 boys) and sixty regular school students (30 girls, and 30 boys) were randomly selected. Assertiveness Scale of Gambrille and Richey, Self–esteem inventory of Coopersmith and the students Grade point average in the last year were used. Results: Analysis of data with utilization of MANOVA, Pearson's correlation coefficient, and Multiple Regression analysis showed that gifted Students were superior in all three measures of assertiveness, self–esteem, and academic achievement. However, there were no difference in terms of these variables in males and females. There was a positive relationship among the three variables in regular school students. In gifted students, a positive significant correlation was observed only between assertiveness and self–esteem. In addition, assertiveness and self–esteem significantly predicted academic achievements of regular school students. Conclusion: The results of this study have been discussed and suggestions for future studies have been given.