Alexithymia has been linked to risky or problematic alcohol use, with a common interpretation invoking deficient emotion regulation and use of alcohol to cope with distress. An alternative explanation positing a general deficit of interoception in alexithymia suggested that poor awareness of internal cues of overconsumption may promote excessive drinking. The present study assessed predictions based on these hypotheses in 337 young adult alcohol users recruited online. Participants completed validated questionnaire indices of alcohol use, alexithymia, emotion regulation, interoceptive sensibility, and sensitivity to reward and punishment. Alcohol use was positively correlated with alexithymia and reward sensitivity, and negatively correlated with emotion regulation as expected, but was uncorrelated with interoceptive sensibility. Alexithymia was not significantly correlated with most dimensions of interoceptive sensibility but was highly negatively correlated with emotion regulation. Hierarchical regression controlling for demographic variables indicated that alexithymia, emotion regulation, sex, and sensitivity to reward and punishment were significant predictors of alcohol use levels. Bootstrapped mediation test controlling for all other variables indicated mediation of the association between alexithymia and alcohol use by deficient emotion regulation but not interoceptive sensibility. Results supported the emotion regulation deficit interpretation of the association of alexithymia with alcohol use. Limitations concerning interoception measurement, online samples, self-report measures, cross-sectional designs, and collection of data during the COVID-19 pandemic are discussed. Future research could follow up on these findings by testing interoceptive accuracy in addition to interoceptive sensibility in relation to alexithymia and alcohol use.