Abstract Background The impact of renal and hepatic dysfunction on the morbidity and mortality of inpatients with adverse drug events (ADEs) is uncertain in daily clinical practice. The objective of this study was to investigate the effect of renal and hepatic function on ADEs and inpatients’ morbidity and mortality. Methods The Japan Adverse Drug Events (JADE) study was a prospective cohort study carried out at three tertiary-care teaching hospitals in Japan. Participants were consecutive inpatients (n=3459) aged 15 years or older. We evaluated the effect of renal and hepatic function on the occurrence of ADEs, and assessed how they affected length of hospital stay (LOS) and in-hospital mortality. We used the estimated glomerular filtration rate to quantify renal function and categorized patients into three groups (normal, ≥60 mL/min/1.73 mm; moderate, ≥30 and <60 mL/min/1.73 mm; severe, <30 mL/min/1.73 mm). We defined patients as having hepatic dysfunction when at least one data point (total bilirubin, aspartate aminotransferase, alanine aminotransferase, or gamma glutamyltransferase) was beyond a cutoff value. Results We analyzed the laboratory data of 2508 patients. There was a significant difference in the occurrence of ADEs among the three GFR categories (normal, 20%; moderate, 26%; severe, 22%; p=0.02). More ADEs occurred in patients with hepatic dysfunction (25% vs. 20%, p=0.01). LOS was significantly longer in those with ADEs stratified either by renal or by hepatic dysfunction (p<0.0001). ADEs were independently associated with in-hospital mortality, adjusting for renal and hepatic function (p<0.0001). Conclusions Inpatients’ organ dysfunction increased ADEs, and ADEs were associated with both LOS and in-hospital mortality independently, irrespective of renal and hepatic function.