A recent study of the impact of smoked cannabis on simulated driver behavior demonstrated a reduction in mean speed after smoked cannabis. Previous research identified an association between personality and individual differences and acute drug effects. The present study examined the impact of personality on the reduction in mean speed after smoking cannabis under single and dual-task driving conditions originally reported by Brands et al. (2019). Sixty-one participants randomly assigned to the active drug condition completed a battery of self-report questionnaires measuring various personality constructs and subsequently operated a driving simulator before and 30 min after smoking a 12.5% Δ9-tetrahydrocannabinol (THC) cigarette. Linear regression modeling tested the influence of self-reported driving errors, lapses, and violations, driver vengeance, psychological distress, impulsivity, and sensation seeking on the reduction in speed after smoking cannabis. After adjusting for the influence of sex, blood THC concentration, and predrug mean speed, impulsivity was a significant predictor of change in speed under both single- (β = −.45, t = −3.94, p <.001) and dual- (β = −.35, t = −2.74, p =.008) task driving conditions after cannabis. Higher trait impulsivity was significantly associated with greater reductions in driving speed after cannabis use, which may reflect greater sensitivity to drug effects and a stronger compensatory response. Further multidisciplinary study, including neurochemical, genetic, and psychological components, would be beneficial in helping to better understand how impulsivity and other personality or individual differences may impact the effects of cannabis on driver behavior and performance.