Nonoperative management of liver injuries (NOMLI) is highly successful and rarely leads to adverse events. Prospective observational study. High-volume academic level I trauma center. For 26 months, 78 consecutive unselected patients with liver injuries were followed up prospectively. In the absence of hemodynamic instability or signs of hollow visceral trauma, NOMLI was offered irrespective of the magnitude of the liver injury. Main Outcome Measure Failure of NOMLI, defined as a laparotomy after an initial decision to treat the patient nonoperatively. Of the 78 patients, 23 (29%) were operated on immediately, but only 12 (15%) for bleeding from the liver. All 12 patients required packing in addition to other maneuvers (hepatorrhaphy [n = 8], resection [n = 4], and liver isolation [n = 1]). Of the remaining 55 patients selected for NOMLI, the method failed in 8 for reasons unrelated to the liver injury: 2 underwent a splenectomy, 1 underwent a nephrectomy, 1 had a small-bowel repair, 1 underwent abdominal decompression for abdominal compartment syndrome, and 3 underwent a nontherapeutic laparotomy. The success rate of NOMLI was 85% (47 of 55 patients), but the liver-specific success rate was 100%. Compared with those in whom NOMLI was successful, patients in whom it failed had a higher Injury Severity Score and underwent more blood transfusions, but they had similar liver injury grades. In total, 66 (85%) of liver injuries did not bleed significantly. No adverse events were attributed to NOMLI. Nonoperative management of liver injuries is safe and effective regardless of the grade of liver injury. Failure of NOMLI is caused by associated abdominal injuries and not the liver. Fluid and blood requirements, the degree of injury severity, and the presence of other abdominal organ injuries may help predict failure.