Major depressive disorder is often accompanied by elevated levels of anger, hostility, and irritability, which may contribute to worse outcomes. The present study is a secondary analysis examining the role of anger/hostility in the treatment response to low-dose aripiprazole added to antidepressant therapy in 225 patients with major depressive disorder and inadequate response to antidepressant treatment. Repeated-measures model demonstrated no drug-placebo difference in treatment response across levels of anger/hostility. However, within-group analyses showed significantly lower placebo response rates in patients with high anger/hostility and a trend for lower drug response rates in patients with high anger/hostility. Pooled response rates across phases and treatments revealed a lower response rate among patients with high anger/hostility. Depressed patients with high anger/hostility demonstrate greater illness severity and lower depressive treatment response rates than patients with low anger/hostility, suggesting that patients with high anger/hostility may have poorer outcomes in response to adjunctive treatment.