The present study aimed to examine intra- and interpersonal associations between poor mental health and mother–daughter relationship closeness in a sample of 467 dyads. An Actor–Partner Interdependence Model was utilized to examine bidirectional processes between mothers (mean age = 42.64, SD = 6.5) and their adolescent daughters (mean age = 15.37, SD = 1.15). The independent variable was self-reported poor mental health and the dependent variable was relationship closeness. Additionally, communication satisfaction was examined as a potential interpersonal mediator of the pathway between poor mental health and relationship closeness. Daughters’ self-reported poor mental health negatively predicted their own perception of closeness as well as mothers’ perception of closeness. Additionally, we find evidence that perceived communication may explain (i.e., mediate) both the actor effect (one’s own poor mental health on one’s own perception of closeness) and the partner effect (partner’s poor mental health on one’s own perception of closeness). Our results suggest that when daughters’ mental health is poor, relationship closeness as perceived by mother and daughter may be weakened, and that this effect may in part be explained by poor communication between mother and daughter. Strategies to promote family communication, especially for families experiencing mental health problems, may aid in the development of closer mother–daughter relationships. Further, our results suggest the importance of investigating the potential bidirectional influence of mothers’ and daughters’ mental health on parent-adolescent relationship quality within a dyadic unit.