We show self control and self image are malleable in adults, and that investments in them reduce crime and violence. We recruited criminally-engaged Liberian men and randomised half to eight weeks of group cognitive behavioural therapy, teaching self control skills and a noncriminal self-image. We also randomised $200 grants. Cash raised incomes and reduced crime in the short-run but effects dissipated within a year. Therapy increased self control and noncriminal values, and acts of crime and violence fell 20–50%. Therapy’s impacts lasted at least a year when followed by cash, likely because cash reinforced behavioral changes via prolonged practice.