Can a moral norm be manipulated and if so, how does a manipulated moral norm interact with a descriptive norm to impact on behavioural intentions? The present research addressed these questions in three studies. Study 1a and 1b demonstrated the validity of a manipulation designed to activate a moral norm for volunteer activity. In Study 2, activating a moral norm for volunteering strengthened intentions to volunteer and inhibited intentions to conform to a descriptive norm. Conceptual and applied implications of activating a moral norm are discussed.