The present study investigates the effectiveness of a family‐based, online media literacy education (MLE) program for substance abuse prevention in children from rural areas. A total of 83 families were randomly assigned to receive Media Detective Family (MDF; n = 47) or a control computer program (n = 36) between pre‐ and posttest questionnaires. A total of 51% (N = 42) completed a 3‐month follow‐up questionnaire. Children receiving MDF reported a significant reduction in their use of substances over time compared to children in the control group (d = −.80). Parents receiving MDF reported that the program was convenient and engaging. The current study showed that an online substance use prevention program using MLE and designed for families is an effective intervention method for reducing children's substance use.