Previous research has shown that perceived parental rejection in childhood has negative effects on psychological adjustment in emerging adulthood. In the context of Interpersonal AcceptanceRejection Theory (IPARTheory), the differentiated sense of self has been proposed as a possible protective factor. Since this outcome results from successful secondary separation-individuation, this study aimed to investigate whether separation-individuation moderates the relationship between parental acceptance-rejection and psychological adjustment in emerging adulthood. Since the separation-individuation process itself can be compromised due to adverse childhood experiences, the possible mediating role of this construct in the relationship between parental rejection and psychological adjustment was also examined. In this study, the responses of 169 female participants aged 18 to 27 years (M = 21.87), which were collected via an online questionnaire, were analyzed. The following instruments were used: Parental Acceptance-Rejection Questionnaire (Rohner & Ali, 2020), Personality Assessment Questionnaire (Rohner & Ali, 2020), and Separation-Individuation Questionnaire for Adolescents (Smojver-Ažić, 1998). It was found that only one dimension of separation-individuation (inhibition due to parental control) acts as a protective factor, mitigating the negative effects of perceived maternal rejection in childhood on current psychological adjustment. Three dimensions of separation-individuation (inhibition due to parental control, need denial, and healthy independence) are significant mediators in the relationship between parental rejection and psychological adjustment. Moreover, paternal rejection contributes significantly and directly to poor psychological adjustment. The findings expand our understanding of the importance of parent-child relationships in childhood, as well as the current separation-individuation, for psychological adjustment in emerging adulthood.