Aim: This study investigates the effect of a participatory organizational intervention on social capital and organizational readiness for change. Design: Cluster randomized controlled trial. Methods: In 2016, 27 departments from five hospitals in Denmark were randomly allocated at the department level to 1 year of participatory intervention (14 clusters, 316 healthcare workers) or a control group (13 clusters, 309 healthcare workers). The participatory intervention consisted of 2 × 2 hr workshops, where managers, 2-5 healthcare workers from each department, and the hospital's health and safety staff, developed action plans for implementing solutions for improving the use of assistive devices at the department throughout the 1-year intervention period. Workplace social capital: (a) within teams (bonding); (b) between teams and nearest leaders (linking A); and (c) between teams and distant leaders (linking B) and organizational readiness for change were measured using questionnaires at baseline, 6, and 12 months. Results: No group-by-time interaction occurred for any of the outcome measures. However, explorative post hoc analysis showed within-group improvements in bonding and linking B social capital and organizational readiness for change following the participatory intervention. Conclusion: Participatory organizational interventions may improve social capital within teams and between teams and distant leaders and organizational readiness for change. Impact: Implementing participatory interventions at the workplace may be a costeffective strategy as they provide additional benefits, e.g., increased social capital and improved organizational readiness for change, that exceed the primary outcome of the intervention. Trial registration: ClinicalTrials.gov (NCT02708550) March 2016.