Introduction: Concomitant multiple substance use by clients in drug abuse treatment settings has been recognized as an important treatment issue for many years, and remains under-researched in Indian context. Aim: To examine the patterns and prevalence of concomitant alcohol and illicit drug use among the patients seeking treatment for illicit drug use. Materials and Methods: A total of 110 patients attending the National drug dependence treatment centre having multiple drug use were included for the present study. Data was collected by face-to-face structured interview on a semi-structured proforma. Results: It was observed that overall 38.2% of the illicit drug users had concomitant alcohol use. Concomitant use of alcohol was found to be 37.1%, 45.5% and 44.4% among heroin, cannabis users and Doda (opium) users respectively. The maximum quantity of alcohol consumption was reported by patients who used opium (Doda) (mean = 703.13 ml/day). A multinomial logistic regression analysis showed that middle aged males and those with lower educational levels, were at greater risk for concomitant exposure to alcohol and illicit drugs. Conclusion: Many people use alcohol in combination with illicit drugs. Clinicians should warn every patient about alcohol-drug interactions, especially those at high risk for concomitant exposure. These findings have implications for prevention, as well as clinical risk for adverse consequences of concomitant alcohol and illicit drug consumption.