Summary According to the OHS practitioners at the Commission des normes, de l'équité, de la santé et de la sécurité du travail (CNESST), nearly 50% of workers with an occupational injury on the island of Montreal are immigrants (or from ethnocultural minority groups) (CNESST, 2010). This is an estimate only, as the CNESST does not collect data on ethnocultural indicators such as country of birth or mother tongue. In the context of the IRSST project titled Understanding the process of rehabilitation and returning to work in the context of intercultural relations (Côté et al., 2017), workers, employers, clinicians and CNESST practitioners were interviewed on the subject of factors hindering and facilitating the return to work. Strategies implemented by clinicians and CNESST practitioners were identified, as well as their needs in terms of developing intercultural competencies. According to the practitioners interviewed, acquiring intercultural competencies can facilitate intercultural communication by improving their interpersonal and active listening skills and their understanding. The aim of this study was to develop content for a support tool designed to improve the intercultural competencies of CNESST practitioners by means of a co-construction process. This study involved co-constructing an intercultural communication support tool for these practitioners (objective 1), documenting the co-construction process used (objective 2), and evaluating the development of intercultural competencies in a group of CNESST practitioners (objective 3). Three groups ‒ a working group composed of 10 practitioners (rehabilitation counsellors and compensation agents) and a facilitator, a validation group comprising 14 practitioners (rehabilitation counsellors and compensation agents), and a steering committee ‒ each met on a regular basis over an 18-month period to conduct collaborative research using a co-construction approach. Several methodological approaches and data collection tools were used to achieve the study’s general objective. First, for objective 1, (a) collaborative research (Desgagné, Chené and Roy, 1997) and (b) the methodology of intercultural situation workshops (Apedaile and Schill, 2008; Mutha, Allen and Welch, 2002; Van Staalduinen, Towle, Godolphin and Laing, 2003; White and Gratton, 2017) were used. For objective 2, (c) participant observation was used during each meeting of the working group and of the steering committee. Next, for objective 3 concerning the development of intercultural competency, (d) the Intercultural Effectiveness Scale (IES) (Portalla and Chen, 2010) and Intercultural Sensitivity Scale (ISS) (Chen and Starosta, 2000) questionnaires were administered to the practitioners, and (e) a focus group was held (with the steering committee). The aim of the co-construction process was to define the form that the intercultural communication support tool should take, as well as its content and pedagogical objectives. As the process was not pre-determined, the study identified the key steps involved, the various issues that might have slowed it down, and the factors facilitating the construction of the intercultural communication support tool. The study measured the progression in the practitioners’ intercultural competency in three observational forums: (a) the working group composed of compensation and rehabilitation professionals; (b) the steering committee composed of managers; and (c) a validation group comprising compensation and rehabilitation professionals. The study shows the importance of integrating the three dimensions ‒ individual, collective and organizational ‒ into the definition of intercultural competency and into the implementation of a collaborative and reflective process on this type of competency in occupational health and safety (OHS) organizations. It also highlights the importance of certain themes serving as the basis for discussion: the meaning of work, pain and work capacity; overqualification; and the different work reintegration patterns or trajectories of immigrants. These themes define major societal issues that extend far beyond the practice framework of work rehabilitation professionals, but they nonetheless remain essential if we are to understand the complex problem of OHS as it affects immigrant workers.