Introduction: The association between peer crowd identification and substance use is well documented among adolescents, but less is known about substance use among young adult peer crowds. Methods: This study leverages data from the Truth Initiative Young Adult Cohort Study (Wave 8, June-July 2015), a nationally representative cohort sample of young adults aged 18-34 years. The current cross-sectional analyses (conducted in 2018) focused on 1,341 individuals aged 18-24 years in this sample. Participants reported their peer crowd identification and current use of alcohol, marijuana, other drugs, and tobacco (cigarettes, little cigars/cigarillos, e-cigarettes, hookah, smokeless tobacco). Adjusted logistic regression models assessed associations between peer crowd identification and substance use. Results: In general, young adults who identified as homebody, young professional, or religious had lower odds of substance use than their counterparts. Young adults who identified as social/ partier were more likely to be current users of alcohol, marijuana, any tobacco, cigarettes, and ecigarettes than those who did not identify as social/partier. Those who identified as alternative were more likely to be current users of marijuana and other drugs than those not identified as alternative. Those who identified as country were more likely than those not identified as country to be current users of cigarettes and smokeless tobacco. Those who identified as hip hop were more likely to be current users of marijuana and e-cigarettes.