Early research has revealed that patterns of aggression and antisocial behavior are present among polydrug users. Often missing from this discourse is the examination of whether polydrug users are quantitatively different from monodrug users in their use of aggression. Theoretical perspectives are often centered on the psychopharmacological effects of substance use on behavior. Consideration of possible poly- versus monodrug use differences and their impact on aggression has not been investigated. Data from this study were derived from a sample of Midwestern university students (N = 793). The relationship between violence, aggression, and concurrent polydrug use in the last year is assessed with a series of multivariate ordinary least squares (OLS) regression models. Results demonstrate that higher incidents of physical and verbal aggression are reported among polydrug users compared to monodrug users and abstainers. When analyses were broken down by polydrug users (those who engaged in alcohol/marijuana and alcohol/NMUPD [nonmedical use of prescription drugs] stimulants), polydrug users reported higher levels of physical aggression compared to monodrug users. Similarly, monodrug users reported higher levels of physical aggression compared to nonusers. This research extends our understanding of aggression among users from two different subcategories: polydrug users in comparison to those who only engage in one form of substance use. Scholars and practitioners who work with violent offenders should consider patterns of drug use behavior when addressing substance use–related aggression.