Aims: To describe the characteristics of hospital-based, patient-mediated interventions and their impact on patient, clinician and organization outcomes. Design: Systematic review. Data Sources: Health literature databases (MEDLINE, CINAHL and EMBASE) were searched in August 2021. Backward and forward citation searching was conducted. Review Methods: Studies investigating patient-mediated interventions, targeted at adult hospitalized patients were eligible. Data were extracted related to study and intervention characteristics. Narrative synthesis was used to understand intervention impact on patient, clinician and organization outcomes (as per a framework). Methodological quality was assessed using the Mixed Methods Assessment Tool. Results: Thirty-three studies, reporting 18 interventions, were included. Twelve interventions prompted patients to report health information about their own health/needs/concerns and six interventions encouraged patients to provide feedback about clinical practice. Across all interventions, there was evidence that patients used patient-mediated interventions and that they may improve patient communication. Healthcare professional outcomes were mixed for actual/intended use, acceptability and usefulness of interventions; yet there was some evidence of healthcare professional behaviour change. Interventions that encouraged patients to report health information about their own health/needs/concerns appeared more successful than other types of interventions. Conclusions: There is some evidence that hospital-based patient-mediated interventions may influence patient communication and healthcare professional behaviour. Patient-mediated interventions that encourage patients to report patient data before a clinical encounter may be more impactful than interventions that encourage patient feedback during or post-encounter. Impact: To date, most patient-mediated intervention research has been conducted in primary care settings; we uncovered the types of patient-mediated interventions that have been trialled in hospitals. We found that patient communication and healthcare professional behaviour may be influenced by these patient-mediated interventions. Future researchers could explore the suitability and effectiveness of a wider range of hospital-based patient-mediated interventions. No patient or public contribution: There was no funding to remunerate a patient/member of the public for this review.