Background: Very high levels of alcohol consumption have been observed in young adult amphetamine-type stimulant (i.e., ecstasy and methamphetamine) users. The reasons for this association are poorly understood. Objective: To examine predictors of hazardous alcohol consumption in a sample of young adult amphetamine-type stimulant users after 30 months of follow-up, controlling for potential confounders. Method: Analysis of longitudinal data from a population-derived sample of Australian young adult amphetamine-type stimulant users (n = 292). A prediction model of alcohol use at 30 months was developed using generalized linear latent and mixed modeling (GLLAMM). Results: Concurrently using ecstasy (Adjusted Odds Ratio [AOR] = 2.67, 95% Confidence Interval [CI] = [1.41, 5.07]), frequently attending nightclubs (AOR = 2.53, 95% CI = [1.04, 6.16]), high baseline alcohol use patterns (AOR = 2.06, 95% CI = [1.32, 3.20]), and being male (AOR = 3.60, 95% CI = [1.48, 8.78]) were associated with an increased likelihood of hazardous alcohol use at 30 months. Conclusion: Concurrent, but not baseline, ecstasy use was associated with hazardous alcohol use, suggesting that combined use of these substances may have an instrumental role in terms of the social functions of drug use (e.g., increasing capacity to drink). Integration of educational interventions concerning alcohol and stimulants is warranted.