This study examined who benefits most from a cognitive behavioral therapy (CBT)-based intervention that aims to enhance return to work (RTW) among employees who are absent due to common mental disorders (CMDs) (e.g., depression, anxiety, or adjustment disorder). We researched the influence of baseline work-related self-efficacy and mental health (depressive complaints and anxiety) on treatment outcomes of two psychotherapeutic interventions. One-year follow-up data of 168 employees were collected, who either received work-focused cognitive behavioral therapy (W-CBT) (n = 89) or regular cognitive behavioral therapy (R-CBT) (n = 79). Compared with R-CBT, W-CBT resulted in a faster partial RTW, irrespective of baseline self-efficacy. Among individuals with high self-efficacy, W-CBT also resulted in faster full RTW. The effectiveness of W-CBT on RTW did not depend on baseline depressive complaints or anxiety. The decline of mental health complaints did not differ between the two interventions, nor depended on baseline self-efficacy or mental health. We recommend W-CBT as a preferred method for employees with CMDs, irrespective of baseline self-efficacy, depression and anxiety. For individuals with high baseline self-efficacy, this intervention also results in higher full RTW. For those with low self-efficacy, extra components may be needed to promote full RTW (download article).