Background and aims Most studies of the association between child maltreatment and subsequent problem alcohol use are retrospective. We studied the association of prospectively substantiated child maltreatment with problem alcohol use in adulthood. Design We used a prospective cohort record linkage correlational design using data from a statutory child protection agency of prospectively substantiated child maltreatment linked to a birth cohort from a major metropolitan maternity hospital. Setting The Mater‐University of Queensland Study of Pregnancy in Brisbane, Australia. Participants Of the 3762 young people at the 21‐year follow‐up, 169 (4.5%) had a history of substantiated maltreatment by 16 years. This was most commonly emotional abuse (n = 90). Measurements The main outcome was heavy alcohol use at the 21‐year follow‐up, defined as four or more standard drinks per day. Secondary outcomes were life‐time and 12‐month diagnoses of alcohol use disorders in  2531 participants who completed the Composite International Diagnostic Interview‐auto (CIDI‐auto) version. Predictor variables were physical, sexual and emotional abuse, as well as neglect. Findings At follow‐up, 407 of the 3762 participants reported heavy alcohol use (10.8%). On adjusted analyses, participants who had experienced emotional abuse were significantly more likely to report heavy alcohol use at the time of interview (adjusted odds ratio = 1.856; 95% confidence interval = 1.038–3.319; P = 0.037). Neglect was associated with a life‐time CIDI diagnosis of an alcohol use disorder. Other types of child maltreatment were not significantly associated with any of the outcomes. Conclusions Prospectively identified experience of childhood emotional abuse and neglect appears to be positively associated with problem alcohol use at age 21.