Illicit substances increase risk of morbidity and mortality and have significant consequences for society. Personality traits are associated with drug use; we test whether these associations vary by socioeconomic status.Participants (N = 412) from the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study completed the Revised NEO Personality Inventory and self-reported use of opiates and cocaine. 50% of participants were living below 125% of the federal poverty line. Mean-level personality differences across never, former, and current opiate/cocaine users were compared. Logistic regressions compared never versus current users and interactions between personality traits and poverty status tested whether these associations varied by socioeconomic status.High Neuroticism and low Agreeableness increased risk of drug use. The association between low Conscientiousness and drug use was moderated by poverty, such that low Conscientiousness was a stronger risk factor for illicit substance use among those with relatively higher SES. For every standard deviation decrease in Conscientiousness, there was a greater than 2-fold increase in risk of illicit substance use (OR = 2.15, 95% CI = 1.45–3.17). Conscientiousness was unrelated to drug use among participants living below 125% of the federal poverty line.Under favorable economic conditions, the tendency to be organized, disciplined, and deliberate is protective against drug use. These tendencies, however, matter less when financial resources are scarce. In contrast, those prone to emotional distress and antagonism are at greater risk for current drug use, regardless of their economic situation.