This paper studies the link between self-image and behavior among those who face stigma due to poverty and social exclusion. Using a randomized field experiment with sex workers in Kolkata (India), we examine whether a psychological intervention to mitigate adverse effects of internalized stigma can induce behavior change. We find significant improvements in participants' self-image, their savings choices, and health clinic visits. Administrative data confirm that these changes in savings and preventive health behavior persist 15 and 21 months later, respectively. Our findings highlight the potential of purely psychological interventions to improve the life choices and outcomes of marginalized groups.