Disruptive behavior disorders (DBDs) are among the primary reasons for child and youth referrals to mental health services and are linked to poor adult outcomes including antisocial behavior disorder. Research indicates a high incidence of internalizing problems in those with DBDs and those who have DBDs with cooccurring internalizing problems may have more severe later outcomes. Interventions targeted at internalizing symptoms have been found to also reduce comorbid externalizing problems. The impact of treatments for DBDs on comorbid internalizing disorders is not known. Databases PsycINFO, EMBASE and MEDLINE were systematically searched based on the Cochrane guidelines for systematic reviews. Records were independently reviewed by two reviewers. 12 papers were deemed eligible. A quality assessment of the selected studies was conducted independently by both reviewers. The 12 studies included 1334 young people with a mean age of 5 years. The parent training interventions assessed were the Incredible Years (6/12 studies), Triple-P (5/12) and Tuning In To Kids (1/12). 11 of the 12 studies reported significant reductions in primary externalizing behavior problems and DBDs. 7 studies reported significant reductions in internalizing symptoms. Mechanisms of change, clinical implications and directions for future research are discussed.