Internalizing problems are common among college students and have been linked consistently to deficits in emotion regulation (ER). Also, hostility/anger (animosity toward others, phenomenological aspect of anger) is an important feature of internalizing problems, but has received limited attention as a mediator between ER and outcomes. Results (N = 160) indicated that although college students' ER abilities corresponded with all three types of internalizing symptoms, hostility/anger mediated fully the relationship for symptoms of depression and social anxiety, but not generalized anxiety (GAD). The stronger interpersonal aspect inherent in depression and social anxiety relative to GAD may in part explain findings, but findings must be viewed in lieu of limitations, which include self-report, a non-clinical sample, and a cross-sectional design. Overall, hostility/anger may be important to address in interventions and programs aimed at reducing internalizing problems, especially among those who demonstrate ER deficits and are prone to depression and social anxiety.