Individuals with substance use (SUD) and/or psychiatric disorders (PD) are disproportionately affected by tobacco use; yet, little is known about secondhand tobacco smoke (SHS) exposure in these populations. An analysis of existing data examined SHS exposure among 497 smokers in community clinics in Vancouver, Canada. Seventy-percent of the participants reported SHS exposure. In sex-stratified multivariate logistic regression analyses correlates of SHS exposure among women were not having a history of using evidence-based smoking cessation treatment and using a single substance (as compared to a polysubstance use history); whereas among men, a history of a respiratory illness and higher nicotine dependence were associated with SHS exposure. Despite limitations about the measures of SHS exposure used in the study, these findings suggest a need to further determine the risks associated with SHS exposure and tobacco use among individuals with SUD and/or PD within mental health and addictions treatment settings.