The FairHealth project brings together researchers from a variety of social sciences and medical disciplines to create a deeper understanding of the processes by which employees’ perceptions of unfair treatment – a psychosocial job stressor – can lead to musculoskeletal disorders (MSDs) over time. MSDs refer to health problems of the locomotor apparatus and include all forms of ill-health ranging from light, transitory disorders to irreversible, disabling injuries. MSDs are among the most common and costly health problems among working populations, and constitute a major cause of disability and social exclusion. Research indicates that MSDs are not a simple consequence of harmful physical exposures, and that psychosocial factors have substantial influence on MSDs. However, the underlying mechanisms through which psychosocial factors can affect MSDs, as well as the contingencies of these processes, are not adequately understood. The objective of FairHealth is to study the time course of unhealthy reactions to perceived injustice, and to produce new and actionable knowledge about whether, why and when injustice at work influences employees’ physical health. The project consists of two observational, prospective cohort studies combined with a longitudinal qualitative investigation. By combining theoretical frameworks and methods stemming from several relevant disciplinary fields, FairHealth is likely to generate significant scientific, economic and social impacts.