Background: There are few evaluations of very early intervention for the prevention of internalising disorders and those that exist generally evaluate outcomes to a maximum of 12 months. The current study evaluated the very long term effects (11 years) of a brief internalising prevention program presented to parents of preschool aged children. Methods: The original sample comprised 146 preschool-aged children who scored high on measures of inhibited temperament. Half of the parents were given a brief educational program (six-sessions) to assist them to help their children reduce anxiousness. Over 70% of the original sample ("n" = 103) was assessed for the current study, which occurred when the sample was approximately 15 years. They were assessed on current diagnoses of anxiety and depression, as well as symptoms of anxiety, depression, negative thoughts, and life interference. Results: Compared with controls, girls whose parents had been through the early intervention program showed significantly fewer internalising disorders, maternally reported anxiety symptoms and self-reported life interference, and trends toward lower self-reported anxiety symptoms and self reported thoughts of loss and failure. Boys showed few differences. Conclusions: A brief early intervention program delivered to parents of preschool-aged children who are at risk for later internalising distress shows lasting benefits for girls into the high-risk period of middle adolescence. Given the low costs associated with this program, these results show promise for strong public health benefits. (Contains 2 tables and 2 figures.)