<p>This study aimed to explore the impact of interparental conflict on adolescents mental health within families characterized by intergenerational caregiving arrangements, as well as the mediating role of the parent-child relationship and the moderating role of the grandparent-grandchild relationship. A total of 3,128 adolescents aged 11–16 years, primarily from families involving intergenerational caregiving, participated in the study. Participants were surveyed using the Interparental Conflict Scale, Parent-Child Relationship Scale, Strength and Difficulties Questionnaire, and Grandparent-Grandchild Relationship Scale. Results indicated that interparental conflict could directly affect adolescent mental health and indirectly influence it through the parent-child relationship. Furthermore, we found grandparent-grandchild relationship played a moderating role between interparental conflict and parent-child relationship, and the stronger grandparent-grandchild relationship mitigated the negative impact of interparental conflict on parent-child relationship. These findings highlight the importance of considering multiple family subsystems when examining adolescents mental health within intergenerational caregiving contexts.</p>