A paucity of research exists in which the co-occurrence of substance use, mental illness, and violence in young adults is examined. Concurrently, there is also a lack of research explicating the contribution of theoretically based risk factors for these problematic outcomes in this population. This lack of both outcome and explanatory research equally affects the utility of theories and interventions for this population. This article utilizes a sample of N = 633 21-year-olds to examine the prevalence of (1) violence and substance use, (2) mental illness (i.e., mood and anxiety disorders) and substance use, and (3) the use of multiple substances and investigates the relationship between various social determinants and said outcomes. Overall, the prevalence rates for the comorbid conditions were low; although on average males had higher rates than did females. Individual attitudes, perceived opportunities, and recent stressful life events were associated with the co-occurrence of outcomes. Implications for behavioral health are explored.