This study uses a multi-method approach to investigate the effectiveness of Parent-Child Interaction Therapy (PCIT) in reducing children's behavior problems when parents report clinical levels of depressive symptoms. Participants were 132 children, 2-7 years of age, and their biological mothers, who either reported low (N = 78) or clinical levels of depressive symptoms (N = 54). Results showed that depressive mothers were likely to report more severe child behavior problems than non-depressive mothers at the pre-treatment assessment, but that depressive mothers reported greater reductions in child behavior problems than non-depressive mothers from pre- to post-treatment. The two groups showed similar levels of observed interaction quality at the pre-treatment assessment (i.e., parent and child emotional availability and parent verbalization patterns) and similar improvements in interaction quality from pre- to post-treatment. The implications of the findings for clinical practice were discussed.