Objective: The objective of the present study was to examine whether exposure to prenatal psychoactive substances is associated with psychological outcomes and deviant behaviour. Methods: This was a secondary analysis of 7,769 mother–child dyads in the Avon Longitudinal Study of Parents and Children (ALSPAC) who were followed until the children were aged approximately 12 years. Parental characteristics and maternal use of various substances were collected in pregnancy and entered as predictors of psychological outcomes in childhood and deviant behaviours in early adolescence. The psychological outcomes were IQ, social cognition, working memory and inhibition, while the deviant behaviours were threatening others, truancy and cruelty to animals. Weighted logistic regression models were used to predict deviant behaviours and weighted linear regression for the psychological outcomes. Results: High prenatal alcohol exposure predicted truancy and cruelty to animals. Tobacco exposure predicted lower IQ, a greater social communication deficit, lower working memory, truancy and threatening others. Illicit drugs predicted a higher social communication deficit and truancy. All prenatal substance exposures remained significant after adjustment for peer influences and covariate imbalance. Conclusion: Alcohol, tobacco and illicit drugs were associated with deviant behaviours in early adolescence and these behaviours were preceded by psychological deficits in childhood. The present study supports the guideline that no amount of alcohol is safe to consume in pregnancy and that tobacco and illicit drugs should be avoided.