This paper studies the link between self-image and behaviour among those who face stigma due to poverty and social exclusion. Using a randomised field experiment with sex workers in Kolkata (India), the authors examine whether a psychological intervention aimed at mitigating the adverse effects of internalised stigma can induce behaviour change. They find significant improvements in participants’ self-image, as well as their savings and preventive health choices. Additionally, changes in savings and health behaviour persist up to 15 and 21 months later respectively. The findings highlight the potential of purely psychological interventions to improve the life choices and outcomes of marginalised groups.