The family is the most important social institution and marriage is its core; therefore, the quality of marital relationships plays a decisive role in mental health, life satisfaction, and family strength. However, the first years of marriage are the most likely to result in conflict due to individual, cultural, and communication differences, and a significant portion of divorces also occur during this period. Research shows that marital conflicts, in addition to reducing satisfaction, trust, intimacy, and mental health, also contribute to the collapse of relationships. Among the factors affecting conflict management, interpersonal trust, self-strength, and psychological flexibility are of particular importance because these variables increase couples' ability to regulate emotions, understand each other, solve problems, and adapt to difficult situations. The theoretical framework of this study is based on mentalization; a capacity that allows individuals to better understand and interpret their own and their spouse's mental states and reduce emotional and defensive reactions. Based on evidence, strengthening mentalization can enhance trust, self-efficacy, and psychological flexibility, and improve conflict management. Despite the effectiveness of this approach in international studies, a local mentalization-based educational package for marital conflict management has not been developed and validated in Iran. Therefore, the present study aims to design and validate a mentalization-based marital conflict management educational package and examine its effectiveness on interpersonal trust, self-efficacy, and psychological flexibility of couples. The innovation of the research is to combine the theoretical foundations of mentalization with the cultural needs of Iranian society and provide a local and practical educational intervention to improve the quality of marital relationships.