BACKGROUND: Fibromyalgia (FM) patients often perceive heightened levels of injustice, which can be associated with depressive symptoms. Despite this connection, the mediating role of depression between perceived injustice and pain intensity in FM patients remains unexplored. AIM: This study explored whether depression mediates the relationship between perceived injustice and pain intensity in FM. METHODS: Data were collected through an online survey distributed to FM patients at the Tel Aviv Sourasky Medical Center, Israel. A total of 161 FM patients completed the survey, with perceived injustice assessed using the Injustice Experience Questionnaire, depression evaluated using the Patient Health Questionnaire, and pain intensity measured with the numerical Pain Intensity Rating Scale. Statistical analyses included analysis of variance and bootstrap-based mediation models. RESULTS: FM patients reported elevated levels of pain, perceived injustice, and depression. The study found that depression significantly mediated the association between perceived injustice and pain intensity in FM patients (P < 0.001, CI = 0.024, 0.312). CONCLUSION: The link between perceived injustice and pain intensity in FM is partially explained by the level of depression. Individuals with higher perceived injustice scores are more susceptible to depression, subsequently experiencing increased pain. These findings suggest that intervention programs targeting depression may mitigate the impact of perceived injustice on pain intensity in FM, potentially enhancing health-related quality of life.