Previous studies have looked at the associations between personality traits and illegal drug use in people across various age groups and in various countries. However, much less is known about how personality traits relate to illegal drug use in young people aged between 16 and 21 in the context of the United Kingdom, who are in a unique developmental period that is more vulnerable to illegal drugs. Moreover, previous studies have only looked at the relationship between personality traits and illegal drug use status, and less much is known about how personality traits relate to drug use frequency. The current study analyzed the data by using a binary and ordinal logistic regression to analyze responses from 775 young drug users and 2757 young non-drug users from UKHLS. The results found that Neuroticism, Openness, and Extraversion are positively related to ever illegal drug use whereas Agreeableness and Conscientiousness are negatively associated with ever illegal drug use during the past year. However, only Agreeableness, Openness, and Conscientiousness were associated with the frequency of illegal drug use. To conclude, the current study contributes to theories that propose illegal drug use is a result of personality traits such as the self-derogation theory and the problem behavior theory, which propose that substance use is a result of personality. Psychologists might use this information as a method to identify potential populations who are at risk of taking illegal drugs, which may benefit preventive interventions that can reduce illegal drug use in young people. Future studies should use more objective measures, examine different types of drug use, and test these associations in other cultures.