BackgroundEvidence shows traditional sexual harm reduction for female sex workers (FSW) based on health behaviour theories is effective but short-lived. This study aimed to evaluate and understand the effectiveness of a resilience-promoting programme in improving psychological health and, ultimately, safe sex practice.MethodsA randomised controlled trial was conducted at three Hong Kong-based non-governmental organisations. 127 sex workers were recruited and randomly assigned to the intervention or control groups. The former received a six-session resilience-promoting programme designed to improve self-esteem, self-efficacy and coping skills, whereas the latter had the usual care. Between-group differences in psychological outcomes and condom use were tested using the intention-to-treat, with ANOVA and chi-square tests, measured at baseline, post-intervention and 3-month follow-ups. Multiple mediation analysis was used to examine how the intervention worked through resilience factors.ResultsSignificant between-group improvements in adaptive coping (F1,119 = 5.82, p < .05) and reduction in psychological distress (F1,118 = 5.00, p < .05) were seen at post-intervention and 3-month follow-ups, with significant time × group interaction changes suggesting the changes occurred at different rates between the two groups. Condom use during the last transactions had increased in the intervention group and the rate of consistent condom use during transactions improved in the intervention group at follow-ups (χ2 = 4.35, p < .05). Self-esteem and resilience significantly mediated the effect of intervention at reducing psychological distress.ConclusionsThese findings suggest that resilience improves the psychological health and general wellbeing of Chinese FSWs.