By the age of 18, girls are more than twice as likely as boys to experience internalizing symptoms. Focusing upon the family, a significant factor for adolescent mental health, we examined how positive and negative daily family interactions relate to gender differences in internalizing symptoms. 681 12th grade students (54 % female) completed diary checklists each night for 2 weeks in which they indicated whether they got along with their family (positive family interactions) and argued with their family (negative family interactions). Results indicate that negative daily family interactions explain, in part, why females experience heightened internalizing symptoms. Yet, even in the face of negative family interactions, positive daily family interactions have salutatory effects, reducing females' emotional distress and eliminating gender differences in internalizing symptoms at high levels of positive interactions. These findings underscore the importance of positive family interactions for adolescent girls' mental health.