Patient safety research has adapted concepts and methods from the workplace safety literature (safety climate, incident reporting) to explain why patients experience unintentional harm during clinical treatment in hospital (adverse events). Consequently, patient safety has primarily been studied through data generated by health care staff. However, because adverse events relate to patient injuries, it is suggested that patients and their families may also have valuable insights for investigating patient safety in hospitals. We conceptualized this idea by proposing that patients are stakeholders in hospital safety who, through their experiences of treatments and independence from institutional culture, can provide valid and supplementary data on unsafe clinical care. In 59 United Kingdom hospitals we investigated whether patient evaluations of care (N = 23,287 surveys) and the safety information contained in health care complaints (N = 2,017, containing 2.5 million words) explained variance in excess patient deaths (hospital mortality) beyond staff evaluations of care (N = 49,302 surveys) and incident reports (N = 242,859). The severity of reports on unsafe clinical behaviors (error and neglect) communicated in patient' health care complaints explained additional variance in hospital-level mortality rates beyond that of staff-generated data. The results indicate that patients provide valid and supplementary data on unsafe care in hospitals. Generalized to other organizational domains, the findings suggest that nonemployee stakeholders should be included in assessments of safety performance if they experience or observe unsafe behaviors. Theoretically, it is necessary to further examine how concepts such as safety climate can incorporate the observations and outcomes of stakeholders in safety. (PsycInfo Database Record (c) 2021 APA, all rights reserved).