Individuals with elevated social anxiety appear particularly vulnerable to marijuana-related problems. In fact, individuals with social anxiety may be more likely to experience marijuana-related impairment than individuals with other types of anxiety. It is therefore important to determine whether constructs particularly relevant to socially anxious individuals play a role in the expression of marijuana-related problems in this vulnerable population. Given that both social avoidance and using marijuana to cope with negative affect broadly have been found to play a role in marijuana-related problems, the current study utilized a new measure designed to simultaneously assess social avoidance and using marijuana to cope in situations previously identified as anxiety-provoking among those with elevated social anxiety. The Marijuana Use to Cope with Social Anxiety Scale (MCSAS) assessed behaviors regarding 24 social situations: marijuana use to cope in social situations (MCSAS-Cope) and avoidance of social situations if marijuana was unavailable. In Study 1, we found preliminary support for the convergent and discriminant validity and internal consistency of the MCSAS scales. In Study 2, we examined if MCSAS scores were related to marijuana problems among those with (n = 44) and without (n = 44) clinically elevated social anxiety. Individuals with clinically meaningful social anxiety were more likely to use marijuana to cope in social situations and to avoid social situations if marijuana was unavailable. Of importance, MCSAS-Cope uniquely mediated the relationship between social anxiety group status and marijuana-related problems. Results highlight the importance of contextual factors in assessing marijuana-related behaviors among high-risk populations.