Individual differences in circadian rhythmic expression, or chronotype, have been shown to relate to a range of outcomes among university students. Students with an evening chronotype have been found to exhibit elevated consumption patterns of psychoactive substances, and to report experiencing poorer subjective sleep quality and more social jetlag relative to intermediate types and morning types. The current study aimed to investigate whether subjective sleep quality and social jetlag might play mechanistic roles in chronotype-substance use associations. Three-hundred and twenty-three first year psychology students from the University of Canterbury completed a questionnaire which included items assessing chronotype, subjective sleep quality, social jetlag, and their consumption patterns of alcohol, cigarettes, electronic nicotine delivery systems, and caffeinated beverages. As hypothesised, evening types participants were more often current smokers and electronic nicotine delivery system users, and consumed cola more frequently relative to other chronotypes. Although there was no evidence for direct effects of eveningness on alcohol and coffee consumption frequency, entirely indirect effects via social jetlag and poor subjective sleep quality, respectively emerged. Findings indicate that elevated substance use among evening types is partially attributable to the mismatch between their delayed circadian rhythms and societal demands, and the poor sleep quality that they experience as a consequence of this.