Parent Training (PT) is not as effective for parents with histories of internalizing symptoms as it is for other parents. This study aimed to determine which dimensions of parenting, notably parenting efficacy, positive parenting, inconsistent discipline, and poor supervision, mediate the association between parent lifetime internalizing symptoms and post-PT child emotional and behavioral difficulties. One hundred fourteen parents (82% biological mothers) of children aged 9-12 years received PT at an urban children’s mental health clinic. Parents reported their lifetime internalizing symptoms, pre- and post- PT parenting skills, and pre- and post- PT child difficulties. Positive parenting fully mediated the relation between parent lifetime internalizing symptoms and elevated child post-PT emotional and behavioral difficulties. Specifically, parents higher in internalizing symptoms reported lower positive parenting post-PT, which in turn predicted more child difficulties post-PT. Findings suggest that fostering positive parenting in PT may be particularly important for parents with histories of internalizing symptoms.