ABSTRACT Objective This study aimed to investigate the relationship among family environment, criminal thinking, and attitudes toward substance use in delinquent adolescents. Methods A descriptive correlational study was conducted. A total of 132 adolescents who arrested for narcotic-related crimes and referred to the Delinquency Rehabilitation Center of Yazd City, Iran, were selected. The data were gathered using the Attitude toward Narcotic Substances questionnaire, the Family Environment Scale, and the Psychological Inventory of Criminal Thinking Styles and were analyzed via the Pearson correlation and multiple regression analysis. Results The findings showed that among the dimensions of family conflict, cohesion, and expressiveness in the family environment, only the family conflict dimension had a significant positive correlation with criminal thinking and positive attitudes toward substance use. There was also a meaningful positive relationship between criminal thinking and positive attitudes toward substance use (p < .01). The results of the regression analysis indicated that only criminal thinking was able to predict the adolescents’ positive attitudes toward substance use, while the family environment did not play any significant predictive role (p > .05). Conclusion In sum, it was concluded that the crimial thinking patterns in adolescents created in interaction with the peer groups were mainly related to positive attitudes toward substance use rather than the family environment.