BACKGROUND: With tightening healthcare budgets, assessing the economic impact of mental health treatments is crucial for informing policy measures. Sociodemographic factors, such as gender, are associated with these outcomes. We studied the gender-specific impact of long-term rehabilitative psychotherapy on the income of working-age individuals who had experienced sick leave due to common mental disorders (CMD). METHODS: We analyzed register data from 2010 to 2019, covering a 33 % random sample of the Finnish working-age population (aged 18-55 in 2010). The sample included 32,558 individuals with their first compensated sickness absence for CMD during 2011-2015. Of these, 4592 (76.1 % women) began psychotherapy, the rest formed the control group. We used difference-in-differences regression with inverse probability weighting to estimate the average treatment effects on the treated (ATT) for women and men relative to the timing of treatment. RESULTS: The average effect was negligible for women (ATT: 0.01, 95 % Confidence Interval: -0.03 - 0.06), while men experienced a substantial 27 % increase in income (ATT: 0.27, 95 % CI: 0.13-0.42). Event-study estimates indicated that the effect on men's income was immediate and long-lasting. LIMITATIONS: Analysis of our findings is restricted to observed register-based covariates including work disability and employment status, and individual- and time-fixed effects. CONCLUSIONS: Among those who had received compensated sick leave due to CMD, men experienced an immediate and long-lasting increase in income after undergoing psychotherapy, while no such effect was observed for women. Further research is needed to explore factors such as selection for treatment, occupational segregation, and treatment engagement among recipients.