Summary Many studies have reported that a strong sense of injustice is associated with a problematic recovery in people with a wide range of debilitating physical and mental health problems. At present, we know little about the determinants of a sense of injustice in the immediate aftermath of a workplace accident, or of changes in the sense of injustice. The primary objective of this research project was to identify the determinants of a sense of injustice in the first few weeks following a workplace accident. The sample of participants included 187 people (92 men and 95 women) who had suffered a disabling musculoskeletal injury because of a work-related incident within the three months preceding the date of enrolment in the study. The participants were recruited through physiotherapy clinics and ads in social media. They were asked to complete online questionnaires three times at three-week intervals. Quantitative and qualitative approaches were used to analyze the data. In a quantitative approach (study 1), scores for standardized pain, depression and disability instruments were used to predict the level of sense of injustice. In a qualitative approach (study 2), participants who had high scores on a standardized instrument measuring sense of injustice (n = 30) were interviewed about the factors that contributed to that feeling. A grounded theory methodology was used to examine the major classes of triggering situations or events that participants had perceived as unjust in the weeks following a workplace accident. The results of study 1 showed that a sense of injustice was common following a musculoskeletal injury. For most participants, scores on the sense of injustice instrument remained stable or decreased during the study period. However, for 23% of the sample, scores on this instrument increased. Cross-sectional regression analyses showed that scores on pain and depression measures contributed significantly to the unique variance of the prediction of sense of injustice scores. The results of lagged cross-sectional regressions suggested that bidirectional effects exist between sense of injustice, pain and depression. Early changes in sense of injustice prospectively predicted later changes in pain and depression, and early changes in pain and depression prospectively predicted later changes in sense of injustice. In study 2, three dominant themes emerged from the interviews: (1) invalidation, (2) undeserved suffering, and (3) blame. Participants described experiences of invalidation on the part of employers, health care professionals and insurance company representatives. Participants’ responses in the interviews also highlighted a sense of injustice resulting from the disruption of their participation in valued daily life activities caused by pain, as well as the expectation of prolonged or permanent pain. Blame is attributed to experiences that contributed to participants’ suffering due to a lack of understanding or recognition or a denial of their condition. The results not only advance our knowledge of the factors contributing to the emergence of a sense of injustice following a disabling injury but also indicate possible avenues whereby perceived injustices may hinder recovery after a workplace accident. The recommended changes in clinical management of musculoskeletal injuries include (1) early screening for a sense of injustice in injured workers; (2) screening for depression in injured workers whose sense of injustice is high; (3) early identification of factors contributing to a sense of injustice in injured workers; (4) development of training modules to reduce invalidating communication; and (5) development of information-based strategies to reduce perceived injustice.