This cross-sectional study describes substance use prevalence and its association with combination antiretroviral therapy (cART) adherence among 3343 individuals receiving care at HIV clinics in Argentina, Brazil, Chile, Honduras, Mexico, and Peru. A rapid screening tool evaluated self-reported 7-day recall of alcohol, marijuana, cocaine, heroin, and methamphetamine use, and missed cART doses. Overall, 29.3 % individuals reported having >/=1 alcoholic drinks, 5.0 % reported any illicit drug use and 17.0 % reported missed cART doses. In the logistic regression model, compared to no substance use, alcohol use [adjusted odds ratio (AOR) = 2.46, 95 % confidence interval (CI): 1.99-3.05], illicit drug use (AOR = 3.57, 95 % CI: 2.02-6.30), and using both alcohol and illicit drugs (AOR = 4.98, 95 % CI: 3.19-7.79) were associated with missed cART doses. The associations between substance use and likelihood of missing cART doses point to the need of targeting alcohol and illicit drug use to improve adherence among people living with HIV in Latin America.