Among marginalized populations, homeless adults are known to have elevated rates of mental health and substance use problems compared to the general population, but less is known about their youthful homeless counterparts. While few studies currently exist, what research has been conducted among street-involved youth has confirmed high rates of comorbidity among this population. However, few of these studies explore predictors of concurrent mental health and substance use problems among street-involved youth and consider broader health and social implications. The aim of the current study was to expand on current knowledge of comorbidity among street-involved youth by examining prevalence and correlates of self-reported concurrent mental health and substance use problems among a sample of 150 street-involved youth in Toronto, Canada. Results of descriptive and bivariate analyses revealed that a quarter of the participants experienced concurrent mental health and substance use problems, and that more youth with concurrent problems had experienced physical child maltreatment, greater transience, street victimization and previous arrest compared to youth without concurrent problems. Logistic regression results showed that street-involved youth with concurrent problems were almost four times more likely to have been victimized in the last 12 months. These results highlight a more disadvantaged health and social profile among street-involved youth with concurrent mental health and substance use problems, and underscore the need for increased research attention on treatment accessibility and needs among this population.