Youth social action—activities such as volunteering, campaigning, and fundraising—has gained traction in the UK and internationally in recent years as governments have supported initiatives to encourage adolescents to develop a ‘habit’ of social action. However, there is not convincing evidence on what a habit of social action is. This study involved a questionnaire with 4518 16–20-year-olds in the UK and finds that moral and civic virtue identity, perceived behavioural control, goal direction, and subjective norms are related to a habit of youth social action. A key contribution of this study is the development and application of a new measure of virtue identity—the Virtue Identity Measure—to which we pay particular attention in this article.