Regret over missed opportunities leads adults to take more risks. Given recent evidence that the ability to experience regret impacts decisions made by 6-year-olds, and pronounced interest in the antecedents to risk taking in adolescence, we investigated the age at which a relationship between missed opportunities and risky decision-making emerges, and whether that relationship changes at different points in development. Six- and 8-year-olds, adolescents and adults completed a sequential risky decision-making task on which information about missed opportunities was available. Children also completed a task designed to measure their ability to report regret when explicitly prompted to do so. The relationship between missed opportunities and risky decision-making did not emerge until 8 years, at which age it was associated with the ability to explicitly report regret, and was stronger in adults than in adolescents. These novel results highlight the potential importance of the ability to experience regret in children and adolescents’ risky decision-making.