Abstract Prolonged sick leaves, particularly those related to common mental disorders (CMDs) and musculoskeletal disorders (MSDs), generate considerable economic and human costs. This issue compels us to improve our understanding of the factors hindering a return to work (RTW) among these two populations. It is well established in the literature that the RTW is the result of a complex interaction between the worker and stakeholders in the various systems, such as the workplace, healthcare and compensation systems. Apart from a few particularities or distinct characteristics, such as the symptoms inherent to a specific disorder or variations in recovery time, the obstacles perceived by individuals suffering from a CMD or an MSD during their RTW process generally overlap, to such a degree that recent research has begun looking at workers on sick leave for either reason as one and the same population, regardless of the nature of their illness or injury. The literature highlights the need to not only evaluate the obstacles perceived during the RTW, but also take into account the worker’s self-efficacy beliefs about overcoming them, two essential notions that complement the evaluation of RTW factors. However, to our knowledge, no tools exist in the literature that are adapted to populations with a CMD or an MSD and that measure both RTW-related obstacles and self-efficacy beliefs about overcoming them. The aim of this prospective study was to validate the tool entitled the Return-to-Work Obstacles and Self-Efficacy Scale (ROSES) with employees involved in the RTW process following a CMD- or MSD-related sick leave. More specifically, it sought to validate the psychometric properties of ROSES: (1) content validity, (2) face validity, (3) construct validity, (4) temporal stability (test-retest reliability) and (5) predictive validity. The study had three phases. First, in Phase 1, the participants who met the inclusion criteria and consented to participate in the study completed the ROSES questionnaire (CMD (n=157) or MSD (n=206)) and a sociodemographic questionnaire. Phase 2 took place one to two weeks later in order to meet the evaluation requirements for test-retest reliability. Lastly, Phase 3, which took place six months after Phase 1, involved evaluating ROSES’ predictive validity by means of regression analyses. All Phase 1 participants were contacted again by telephone to find out whether or not they had returned to their job. Content and face validities. The initial version of ROSES included 97 items divided into six main conceptual categories. Construct validity. Based on the factor analyses (exploratory and confirmatory) and internal consistency analyses performed on the previously constructed conceptual categories, a total of 46 items divided among ten dimensions emerged: (1) fears of a relapse, (2) cognitive difficulties, (3) medication-related difficulties, (4) job demands, (5) feeling of organizational injustice, (6) difficult relations with the immediate supervisor, (7) difficult relations with co-workers, (8) difficult relations with the insurance company, (9) difficult work/life balance and (10) loss of motivation to return to work. Reliability. The results of the correlation analyses showed that the ten dimensions remained stable over time (two weeks) in both populations (CMD and MSD). Predictive validity. In addition to the number of weeks of sick leave and perceived level of pain, four dimensions (perceived obstacles and self-efficacy beliefs) predicted the RTW of the individuals with an MSD: fears of a relapse, job demands, feeling of organizational injustice and difficult relations with the immediate supervisor. For the individuals with a CMD, only job demands and cognitive difficulties emerged as significant. In conclusion, this study validated the ROSES tool. It also filled a theoretical gap in the literature by showing that both biopsychosocial obstacles and self-efficacy beliefs about overcoming them should be taken into account in predicting the RTW of individuals with a CMD or an MSD. On the clinical level, the study offers health professionals the opportunity to work with a valid, quickly administered tool – 46 items covering ten dimensions – that will enable them to systematically assess these two notions in their clients. They will then be able to optimize their interventions to facilitate their clients’ RTW. ROSES thus constitutes a working tool that facilitates dialogue for both parties. Once the dimensions of the paired “problematic” items (obstacles and self-efficacy beliefs) have been identified, health professionals can initiate a discussion with their clients and adopt pertinent interventions and strategies. Lastly, they will be able to use ROSES as a follow-up tool if certain obstacles disappear or persist in the client’s work environment or personal life.