This study reports an experiment designed to test whether self-affirmation can overcome defensive processing of risk information in a sample of UK adult smokers with low socioeconomic status. Participants (N = 57) were randomized to either a self-affirmation or control condition before reading a government-sponsored antismoking leaflet and completing measures of message acceptance, intention, and self-efficacy. Participants' subsequent behavior (taking leaflets) was recorded surreptitiously. Results showed that the manipulation significantly increased message acceptance, intention and behavior, and that the effects of the manipulation on behavior were mediated through message acceptance and intention. The practical and theoretical implications of the findings are discussed in relation to the possible use of self-affirmation manipulations to enhance the effectiveness of smoking cessation interventions.