The aim of this research was to investigate the relationship between assertiveness, responsibility and self differentiation, in female students. Research method has been correlation, and 100 female students were selected randomly as a research sample, They completed assertiveness (AS), responsibility (RS), and self differentia t ion (SDS) questionaires, The results of Pearson correlation showed a positive and significant relationship between assertiveness and self differentiation (P<0.01) and positive relationship between self differentiation and responsibility (P<0.01), Results of stepwise regression analysis showed that assertiveness and responsibility could explain 18% of variance o f s e lf differentiation, . So, self-differentiation could be known as a function of responsibility and assertiveness.