Somaye Kazemian , Ebrahim Naeimi Aim: This study aims to investigate the characteristic of assertiveness of mothers of delinquent adolescents. Method: The statistical population of the study consists of mothers of adolescents with delinquency living in Tehran. Convenience sampling was used to select study participants. The sample size was 15 people in each group (treatment and control groups). Consistent with qualitative research methodology, semi-structured interviews were used for collecting data about participants’ assertiveness. The resulting data from description of interaction between the couples were analyzed using phenomenological theory. Results: What was seen in studying the quality of assertiveness in mothers with delinquent adolescents included: a). withdrawn with care for others (others’ interests – following, accepting others’ talks, escaping response, playing victim), b). aggression with focus on self (dogmatic, uncaring, argumentative, dependence, competition as opposed to cooperation), c). withdrawal and submission to situation and conditions (hopeless, not believing self, blaming others, taking roles), d). withdrawal and parental role ambiguity (indecisive, lack of monitoring - unorganized monitoring, imbalance in motivation for daring behaviors – easy-taking, uncaring. Conclusions: The data from qualitative interviews were analyzed using three stages of open, axial, and selective coding. The results showed that, in the sample under study, most mothers of delinquent adolescents tended to be more passive and less assertivene.