Background & Aims: The utility of liver biopsy in diagnosing or staging idiosyncratic drug-induced liver injury (DILI) is unclear. The aim of this study was to determine whether liver histology impacted causality assessment in suspected DILI using a novel simulation model. Methods: Fifty patients enrolled in the DILI Network (DILIN) who had liver biopsies performed within 60 days of DILI onset were randomly selected. All had standard DILIN consensus causality scoring using a 5-point scale (1=definite, 2=highly likely, 3=probable, 4=possible, 5=unlikely) based on 6-month post-injury data. Three experienced hepatologists independently performed a causality assessment using redacted case records, with the biopsy and selected post-biopsy laboratory data removed. The 3 hepatologists also reviewed the liver histology with a hepatopathologist and then repeated causality assessment for each case. Results: Of the 50 cases, there were 42 high causality DILI cases (1, 2 or 3) and 8 low causality cases (4 and 5). The hepatologists judged that liver biopsy was indicated in 62% of patients; after histology review, biopsy was judged to have been helpful in 70% of patients. Histology review changed the causality score in 68% of patients, with an increase in DILI likelihood in 48% and a decrease in 20%. Biopsy results changed diagnostic certainty from less certain (3 or 4) to highly certain (1, 2 or 5) in 38% of patients. Conclusions: Liver histologic findings may help clarify the diagnosis of DILI. Histology appears to be particularly helpful in cholestatic or equivocal cases of DILI (possible or probable), shifting assessment toward a greater or lower certainty of a DILI diagnosis. Lay summary: The utility of liver biopsy in diagnosing or staging idiosyncratic drug-induced liver injury (DILI) is unclear. Herein, we show that, in patients with suspected DILI, a liver biopsy can help physicians diagnose DILI or other causes of liver injury with more certainty.